Re: Over 30 types of variables available in python ?

[chaouche yacine]

Thanks for all your comments. It appears to me that there is a slight confusion 
between types and classes then, plus other entities (protocols ?)

So my question is : is there a notion of "type" in python, like in other 
languages  (integers, booleans, floats, strings, characters (in c)) ? if so, 
can you give a list of the available "types" ? 


The documentation (http://docs.python.org/2/library/stdtypes.html) states "The 
principal built-in types are numerics, sequences, mappings, files, classes,
instances and exceptions."







 From: Terry Reedy 
To: python-list@python.org 
Sent: Monday, January 7, 2013 1:45 AM
Subject: Re: Over 30 types of variables available in python ?
 
On 1/6/2013 6:12 PM, chaouche yacine wrote:
> 
> booleans
> ints, floats, longs, complexes
> strings, unicode strings
> lists, tuples, dictionaries, dictionary views, sets, frozensets,
> buffers, bytearrays, slices
> functions, methods, code objects,modules,classes, instances, types,
> nulls (there is exactly one object of type Null which is None),
> tracebacks, frames
> generators, iterators, xranges,
> files,
> memoryviews,
> context managers,
> 
> These are all listed in this page
> http://docs.python.org/2/library/stdtypes.html as built-in types.

They would better be called classes. Every thing is Python is an instance of a 
class. 'Iterator' and 'context manager' are protocols that multiple classes can 
follow, not classes themselves.

> Am I
> getting anything wrong here ? I'm a bit confused about it. I have never
> seen so many types in the few programming languages I saw.

C has up to 8 integer types, Python 3 just 1. Most of the above are structures 
in C, which may or may not by typedef-ed, or classes in C++. If you counted all 
the structures and classes that come with C or C++, you would find a comparable 
number.

C stdlib has a pointer to file structure type, which is equivalent to Python's 
file class. It is true that C does not come with hashed arrays (sets) and 
hashed associative arrays (dicts), but they are often needed. So C programmers 
either reinvent the wheel or include a third-party library. C also has frame 
structure, but they are normally hidden. C programmers do not have easy direct 
access. However, virus writers learn to work with them ;-(.

-- Terry Jan Reedy

-- http://mail.python.org/mailman/listinfo/python-list-- 
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Re: os.path.realpath(path) bug on win7 ?

[iMath]

在 2013年1月7日星期一UTC+8上午7时40分06秒，Victor Stinner写道：
> It looks like the following issue:
> 
> http://bugs.python.org/issue14094
> 
> Victor
> 
> Le 6 janv. 2013 07:59, "iMath" <22815...@qq.com> a écrit :
> 
> 
> 
> 
> os.path.realpath(path)  bug on win7 ?
> 
> Temp.link is a Symbolic link
> Its target location is C:\test\test1
> But 
> >>> os.path.realpath(r'C:\Users\SAMSUNG\Temp.link\test2')
> 'C:\\Users\\SAMSUNG\\Temp.link\\test2'
> 
> 
> I thought the return value should be ' C:\\test\\test1\\test2'
> 
> Is it a bug ? anyone can clear it to me ?
> 
> 
> --
> 
> http://mail.python.org/mailman/listinfo/python-list
perhaps it is
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Re: how to detect the character encoding in a web page ?

[iMath]

在 2012年12月24日星期一UTC+8上午8时34分47秒，iMath写道：
> how to detect the character encoding  in a web page ?
> 
> such as this page 
> 
> 
> 
> http://python.org/

up to now , maybe chadet is the only way to let python automatically do it .
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Re: regular expression : the dollar sign ($) work with re.match() or re.search() ？

[iMath]

在 2012年9月26日星期三UTC+8下午3时38分50秒，iMath写道：
> I only know  the dollar sign ($) will match a pattern from the
> 
> end of a string,but which method does it work with ,re.match() or re.search() 
>  ？

I thought re.match('h.$', 'hbxihi') will match ‘hi’ ,but it does not .so why ?
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Re: pyodbc utf-8

[Markus Christen]

When i look at my output on my webpage, i can see this:
W\xe4denswil
but it have to be this:
Wädenswil
you know now what i can see exactly... im using django and they told me its a 
python problem with utf-8. when i turn off debug, i cant see the page, it give 
me an error 500.
the text "Danke für die..." on the bottom of my page is displayed correct. the 
error comes only when an umlaut is to post, out of the raw.
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Re: Over 30 types of variables available in python ?

[Steven D'Aprano]

On Mon, 07 Jan 2013 00:53:26 -0800, chaouche yacine wrote:

> Thanks for all your comments. It appears to me that there is a slight
> confusion between types and classes then, plus other entities (protocols
> ?)


In Python 3, types and classes are synonyms. They mean the same thing.

In Python 2, there is a very subtle difference, due to the existence of 
"old style" or "classic" classes, for backward compatibility, which are 
not identical to "new style" classes, also known as types. But they are a 
"kind of type" -- although there are some differences, you can consider 
them to be the same sort of thing.


> So my question is : is there a notion of "type" in python, like in other
> languages  (integers, booleans, floats, strings, characters (in c)) ? if
> so, can you give a list of the available "types" ?

Yes, and no.

Yes, there is a notation of type in Python which is exactly the same sort 
of notation of type in other languages, such as C. The difference between 
C and Python is not in the notation of "type", but in the notation of 
"variable" or "name".

In C, *variables* have a type. If you declare a variable x to be a float, 
then three things happen:

* the C compiler creates a fixed memory location and calls it "x";

* the C compiler interprets the *value* of that memory location (which is 
actually just a bunch of bytes) as a float;

* the C compiler will only ever place values into that memory location if 
it thinks that the value is a float, or compatible with a float.

Because all values are bunches of bytes, you can (with a bit of effort) 
grab the bytes from any location, without caring what the type the 
compiler considers it. Sometimes this is useful; more often it is a 
source of bugs.

In Python, *names* have no type, but *objects* (values) do. Because names 
are untyped, the one name (say, x) might be store a float one minute, 
then later have a list assigned to it, then a string, then a float again. 
But at any instant, whatever the value of x, it is an object, and objects 
always have a type no matter what name they are bound to. The type 
information is *part of the object*, rather than part of the name.

Because Python considers all objects to be typed, there is no concept of 
extracting the raw bytes from a list. (Of course lists actually are made 
out of bytes, but you cannot access them from pure Python code.)


So, yes, Python has types, just as C has types, but the difference is 
that Python associates the type with the *value* (object) rather than a 
storage location (variable).


But no, we can't give a complete list of all types, because there is no 
limit to the number of types. There are a certain number of built-in 
types, plus many more types which are available from the standard 
library, plus an infinite number of custom types you can create yourself.

You can get a list of the common built-in types and the standard library 
types from the Fine Manual:

http://docs.python.org/2/library/

See also:

http://docs.python.org/2/reference/datamodel.html


There are also built-in types which are essentially undocumented, and 
used as implementation details of higher-level objects like functions, 
methods, and so forth. You are not expected to use these directly. 
Instead, you just use the function itself.


If you are unfamiliar with Object Oriented Programming, you can broadly 
speaking consider types to be like smart structs that carry code around 
with them. There is no limit to the number of possible structs, and 
likewise there is no limit to the number of possible types.


> The documentation (http://docs.python.org/2/library/stdtypes.html)
> states "The principal built-in types are numerics, sequences, mappings,
> files, classes, instances and exceptions."

Yes, they are the principal types, but there are many others.

There are three different built-in numeric types:

int
long
float

plus Decimal and Fraction in the standard library;

There are two standard built-in sequence types:

list
tuple

plus others in the standard library, such as namedtuple;

There is one standard built-in mapping type:

dict

plus at least two more in the standard library, defaultdict and 
ordereddict;

etc. You can read the docs more easily than I can copy the types out.



-- 
Steven
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License status of pycollada?

[Gene Heskett]

Greetings all;

Trying to collect all the dependencies of FreeCad-0.13, but it appears that 
pycollada is behind some sort of a login/paywall on github.  Is anyone here 
familiar with how that works?

Thanks.

Cheers, Gene
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page:  is up!
My views 

Mr. Cole's Axiom:
The sum of the intelligence on the planet is a constant; the
population is growing.
I was taught to respect my elders, but its getting 
harder and harder to find any...
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RE: Numpy outlier removal

[Joseph L. Casale]

> In other words: this approach for detecting outliers is nothing more than 

> a very rough, and very bad, heuristic, and should be avoided.

Heh, very true but the results will only be used for conversational purposes.
I am making an assumption that the data is normally distributed and I do expect
valid results to all be very nearly the same.

> You can read up more about outlier detection, and the difficulties 
> thereof, here:


I much appreciate the links and the thought in the post. I'll admit I didn't
realize outlier detection was as involved.


Again, thanks!
jlc
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Re: regular expression : the dollar sign ($) work with re.match() or re.search() ？

[Steven D'Aprano]

On Mon, 07 Jan 2013 01:45:58 -0800, iMath wrote:

> 在 2012年9月26日星期三UTC+8下午3时38分50秒，iMath写道：
>> I only know  the dollar sign ($) will match a pattern from the
>> 
>> end of a string,but which method does it work with ,re.match() or
>> re.search()  ？
> 
> I thought re.match('h.$', 'hbxihi') will match ‘hi’ ,but it does not .so
> why ?


re.match only matches at the *start* of the string, so "h.$" tries to 
match:

* start of string
* literal h
* any character
* end of string


You want re.search, which will search the entire string and match "hi" at 
the end of the string.


-- 
Steven
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Re: running multiple django/bottle instances

[andrea crotti]

Not really, on the staging server we are using the django/bottle webserver..

Anyway I was thinking that a great possible solution might be to set
up something like buildbot to:
- checkout all the needed branches

- run the various servers for all of them on different ports, where maybe the
  mapping  port-branch is set from somewhere

- run all the unit tests for them and make the results available

With a similar configuration we would probably be very happy already,
anyone doing something similar?

2013/1/7 Michel Kunkler :
> As you are certainly running a production server like Apache, your problem
> is actually not Python related.
> If you want to run your applications on different ports, take a look on e.g.
> Apaches virtual host configurations.
> http://httpd.apache.org/docs/2.2/vhosts/examples.html
>
> Am 03.01.2013 17:35, schrieb Andrea Crotti:
>
>> I'm working on a quite complex web app that uses django and bottle
>> (bottle for the API which is also restful).
>>
>> Before I came they started to use a staging server to be able to try out
>> things properly before they get published, but now we would like to have
>> the possibility to see multiple branches at a time.
>>
>> First we thought about multiple servers, but actually since bottle and
>> django can be made to run on different ports, I thought why not running
>> everything on one server on different ports?
>>
>> We also use elasticsearch and couchdb for the data, but these two
>> don't change that much and can just be a single instance.
>>
>> So what would be really great could be
>>
>> staging_server/branch_x
>> staging_server/branch_y
>>
>> and something keeps track of all the various branches tracked, and run
>> or keeps running bottle/django on different ports for the different
>> branches.
>>
>> Is there something in the wonderful python world which I could bend to
>> my needs?
>>
>> I'll probably have to script something myself anyway, but any
>> suggestions is welcome, since I don't have much experience with web
>> stuff..
>
>
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Re: License status of pycollada?

[Chris Rebert]

On Sunday, January 6, 2013, Gene Heskett wrote:

> Greetings all;
>
> Trying to collect all the dependencies of FreeCad-0.13, but it appears that
> pycollada is behind some sort of a login/paywall on github.  Is anyone here
> familiar with how that works?
>

Er, what? The repo seems freely browseable.
Looks like it's under a standard 3-clause BSD-style license:
https://github.com/pycollada/pycollada/blob/master/COPYING


-- 
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Chris
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Re: Over 30 types of variables available in python ?

[Duncan Booth]

chaouche yacine  wrote:

> 
> booleans
> ints, floats, longs, complexes
> strings, unicode strings
> lists, tuples, dictionaries, dictionary views, sets, frozensets,
> buffers, bytearrays, slices functions, methods, code
> objects,modules,classes, instances, types, nulls (there is exactly one
> object of type Null which is None), tracebacks, frames generators,
> iterators, xranges, files,
> 
> memoryviews,
> context managers,
> 
> These are all listed in this page
> http://docs.python.org/2/library/stdtypes.html as built-in types. Am I
> getting anything wrong here ? I'm a bit confused about it. I have
> never seen so many types in the few programming languages I saw. 

Instances aren't types (though types themselves are instances): every 
object in Python is an instance.

If you want a list of types that exist in your particular copy of Python 
then you can print it out easily enough:


def allsubclasses(base):
mod = base.__module__
if mod in ('builtins', '__builtin__', 'exceptions'):
yield getattr(base, '__qualname__', base.__name__)
else:
yield "{}.{}".format(base.__module__, getattr(base, 
'__qualname__', base.__name__))
for typ in type.__subclasses__(base):
for t in allsubclasses(typ): yield t

all_types = sorted(set(allsubclasses(object)), key=str.lower)
print(len(all_types))
print(all_types)


That won't show any types that haven't been imported, but it gives me  
293 types that are all loaded on startup in Python 3.3 and 150 in Python 
2.7.

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what’s the difference between socket.send() and socket.sendall() ?

[iMath]

what’s the difference between socket.send() and socket.sendall() ?


It is so hard
for me to tell the difference
between them from the python doc

so what is the difference between them ?

and each one is suitable for which case ?-- 
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"Gangnam Style" in line for UK dictionary inclusion

[Constantine]

"Gangnam Style" in line for UK dictionary inclusion 
http://adf.ly/2836760/news.yahoo.com/gangnam-style-line-uk-dictionary-inclusion-134517741.html
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Re: Problem with Unicode char in Python 3.3.0

[Franck Ditter]

In article ,
 marduk  wrote:

> On Sun, Jan 6, 2013, at 11:43 AM, Franck Ditter wrote:
> > Hi !
> > I work on MacOS-X Lion and IDLE/Python 3.3.0
> > I can't get the treble key (U1D11E) !
> > 
> > >>> "\U1D11E"
> > SyntaxError: (unicode error) 'unicodeescape' codec can't 
> > decode bytes in position 0-6: end of string in escape sequence
> > 
> 
> You probably meant:
> 
> >>> '\U0001d11e'
> 
> 
> For that synax you must use either '\u' or '\U' (i.e.
> specify either 4 or 8 hex digits).
> 
> http://docs.python.org/2/howto/unicode#unicode-literals-in-python-source-code

<<< print('\U0001d11e')
Traceback (most recent call last):
  File "", line 1, in 
print('\U0001d11e')
UnicodeEncodeError: 'UCS-2' codec can't encode character '\U0001d11e' 
in position 0: Non-BMP character not supported in Tk
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Re: Problem with Unicode char in Python 3.3.0

[Chris Angelico]

On Mon, Jan 7, 2013 at 11:57 PM, Franck Ditter  wrote:
> <<< print('\U0001d11e')
> Traceback (most recent call last):
>   File "", line 1, in 
> print('\U0001d11e')
> UnicodeEncodeError: 'UCS-2' codec can't encode character '\U0001d11e'
> in position 0: Non-BMP character not supported in Tk

That's a different issue; IDLE can't handle non-BMP characters. Try it
from the terminal if you can - on my Linux systems (Debians and
Ubuntus with GNOME and gnome-terminal), the terminal is set to UTF-8
and quite happily accepts the full Unicode range. On Windows, that may
well not be the case, though.

ChrisA
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Re: Problem with Unicode char in Python 3.3.0

[Terry Reedy]

On 1/7/2013 7:57 AM, Franck Ditter wrote:


<<< print('\U0001d11e')
Traceback (most recent call last):
   File "", line 1, in 
 print('\U0001d11e')
UnicodeEncodeError: 'UCS-2' codec can't encode character '\U0001d11e'
in position 0: Non-BMP character not supported in Tk


The message comes from printing to a tk text widget (the IDLE shell), 
not from creating the 1 char string. c = '\U0001d11e' works fine. When 
you have problems with creating and printing unicode, *separate* 
creating from printing to see where the problem is. (I do not know if 
the brand new tcl/tk 8.6 is any better.)


The windows console also chokes, but with a different message.

>>> c='\U0001d11e'
>>> print(c)
Traceback (most recent call last):
  File "", line 1, in 
  File "C:\Programs\Python33\lib\encodings\cp437.py", line 19, in encode
return codecs.charmap_encode(input,self.errors,encoding_map)[0]
UnicodeEncodeError: 'charmap' codec can't encode character '\U0001d11e' 
in posit

ion 0: character maps to 

Yes, this is very annoying, especially in Win 7.

--
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Re: what’s the difference between socket.send() and socket.sendall() ?

[Thomas Rachel]

Am 07.01.2013 11:35 schrieb iMath:

what’s the difference between socket.send() and socket.sendall() ?

It is so hard for me to tell the difference between them from the python doc

so what is the difference between them ?

and each one is suitable for which case ?



The docs are your friend. See

http://docs.python.org/2/library/socket.html#socket.socket.sendall

| [...] Unlike send(), this method continues to send data from string
| until either all data has been sent or an error occurs.

HTH,

Thomas
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Re: "Gangnam Style" in line for UK dictionary inclusion

[GadgetSteve]

On Monday, January 7, 2013 12:50:00 PM UTC, Constantine wrote:
> "Gangnam Style" in line for UK dictionary inclusion 
> http://adf.ly/2836760/news.yahoo.com/gangnam-style-line-uk-dictionary-inclusion-134517741.html

And this has to do with python how?
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Re: "Gangnam Style" in line for UK dictionary inclusion

[Dave Angel]

On 01/07/2013 08:22 AM, GadgetSteve wrote:
> On Monday, January 7, 2013 12:50:00 PM UTC, Constantine wrote:
>> Trying to get control:   
>> http://AboutToTrashYou.invalid/2892929384736760/news.yahoo.com/Whatever-you-like-it-wont&44work134517741.html
> And this has to do with python how?

When replying to obvious spam, please don't quote the original link
(unless you thoroughly mangle it).  That just doubles the exposure so
more people are likely to click there.

adfly is a well-known adware virus/trojan/annoyance.  People on Windows
machines may have to remove the crud it installs.





-- 

DaveA

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Re: Over 30 types of variables available in python ?

[marduk]

So I guess if one *really* wanted to compare C variables to Python
variables, you could say that all python variables are of type void*
except Python does all mallocs/frees and the casting for you.
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Re: Over 30 types of variables available in python ?

[Dave Angel]

On 01/07/2013 09:32 AM, marduk wrote:
> So I guess if one *really* wanted to compare C variables to Python
> variables, you could say that all python variables are of type void*
> except Python does all mallocs/frees and the casting for you.

A better analogy would be to C++, and all names would be something like 
shared_ptr.  And (except for old-style classes) all actual data
is of a type derived from object.





-- 

DaveA

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Re: Over 30 types of variables available in python ?

[Chris Angelico]

On Tue, Jan 8, 2013 at 1:45 AM, Dave Angel  wrote:
> On 01/07/2013 09:32 AM, marduk wrote:
>> So I guess if one *really* wanted to compare C variables to Python
>> variables, you could say that all python variables are of type void*
>> except Python does all mallocs/frees and the casting for you.
>
> A better analogy would be to C++, and all names would be something like
> shared_ptr.  And (except for old-style classes) all actual data
> is of a type derived from object.

But yes, a C pointer variable is closest to a Python local, with
actual content always stored on the heap.

ChrisA
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Re: Numpy outlier removal

[Oscar Benjamin]

On 7 January 2013 05:11, Steven D'Aprano
 wrote:
> On Mon, 07 Jan 2013 02:29:27 +, Oscar Benjamin wrote:
>
>> On 7 January 2013 01:46, Steven D'Aprano
>>  wrote:
>>> On Sun, 06 Jan 2013 19:44:08 +, Joseph L. Casale wrote:
>>>
>>> I'm not sure that this approach is statistically robust. No, let me be
>>> even more assertive: I'm sure that this approach is NOT statistically
>>> robust, and may be scientifically dubious.
>>
>> Whether or not this is "statistically robust" requires more explanation
>> about the OP's intention.
>
> Not really. Statistics robustness is objectively defined, and the user's
> intention doesn't come into it. The mean is not a robust measure of
> central tendency, the median is, regardless of why you pick one or the
> other.

Okay, I see what you mean. I wasn't thinking of robustness as a
technical term but now I see that you are correct.

Perhaps what I should have said is that whether or not this matters
depends on the problem at hand (hopefully this isn't an important
medical trial) and the particular type of data that you have; assuming
normality is fine in many cases even if the data is not "really"
normal.

>
> There are sometimes good reasons for choosing non-robust statistics or
> techniques over robust ones, but some techniques are so dodgy that there
> is *never* a good reason for doing so. E.g. finding the line of best fit
> by eye, or taking more and more samples until you get a statistically
> significant result. Such techniques are not just non-robust in the
> statistical sense, but non-robust in the general sense, if not outright
> deceitful.

There are sometimes good reasons to get a line of best fit by eye. In
particular if your data contains clusters that are hard to separate,
sometimes it's useful to just pick out roughly where you think a line
through a subset of the data is.


Oscar
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Re: what’s the difference between socket.send() and socket.sendall() ?

[Steven D'Aprano]

On Mon, 07 Jan 2013 18:35:20 +0800, iMath wrote:

> what’s the
> difference between socket style="font-size: 12pt; ">.send() and socket.sendall()
> ? 


Please re-send your question as text, instead of as HTML (so-called "rich 
text"). Since many people are reading this forum via Usenet, sending HTML 
is considered abusive. This is a text newsgroup, not a binary newsgroup.

If you *must* use a client that sends HTML, please make sure that it 
ALWAYS sends a plain text version of your message as well. But here are 
eight reasons you should not rely on fancy formatting (colours, fonts, 
bold, etc.) in text-based media such as email (or news):

- HTML code in email is one of the top 3 signs of spam. Many people
  send "rich text" email straight to the trash as a way of eliminating
  spam.

- HTML code in email is a privacy and security risk. For example,
  that means that the sender can track whether or not you have read
  the email using "web bugs" whether or not you consent to being
  tracked. There are viruses, spyware and other malware that can be
  transmitted through HTML code in email. For this reason, many
  people filter HTML email straight to the trash.

- HTML code forces your choice in font, font size, colours, etc. on
  the reader. Some people prefer to read emails using their own
  choice of font rather than yours, and consider it rude for others
  to try to force a different font. Sending white text on coloured 
  background is especially nasty, because it hurts readability of
  even for people with perfect vision.

- Even if readers don't mind the use of "rich text" in principle, in
  practice once they have received enough emails with pink text on a
  purple and yellow background with blinking stars and dancing fairies
  all over the page, in pure self-defence they may disable or delete 
  HTML emails.

- Use of colour for emphasis discriminates against the approximately
  10% of the male population who are colour-blind.

- Use of italics or other formatting may discriminate against those 
  who are blind and using screen readers to "read" their email. I 
  once was on a maths mailing list for about three years before I
  realised that the most prolific and helpful person there was as 
  blind as a bat.

- Programming is a *text-based* activity. Code depends on WHAT you
  write, not its colour, or the font you use, or whether there are
  smiley faces in the background winking at you. So especially in
  programming circles, many people find HTML code in emails to be a
  distraction and an annoyance. Being able to express yourself in 
  plain text without colours and fonts is a good practice for any
  programmer to get used to.

- Even if you think that people who dislike HTML emails are wrong, or
  silly, or being precious, or completely nuts, nevertheless you should
  indulge us. You are asking for free advice. It does not pay for you to
  offend or annoy those you are asking for help. 


(Apologies to anyone on the "tutor" mailing list who has already seen 
this message earlier today.)



-- 
Steven
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Re: Numpy outlier removal

[Robert Kern]

On 07/01/2013 15:20, Oscar Benjamin wrote:

On 7 January 2013 05:11, Steven D'Aprano
 wrote:

On Mon, 07 Jan 2013 02:29:27 +, Oscar Benjamin wrote:


On 7 January 2013 01:46, Steven D'Aprano
 wrote:

On Sun, 06 Jan 2013 19:44:08 +, Joseph L. Casale wrote:

I'm not sure that this approach is statistically robust. No, let me be
even more assertive: I'm sure that this approach is NOT statistically
robust, and may be scientifically dubious.


Whether or not this is "statistically robust" requires more explanation
about the OP's intention.


Not really. Statistics robustness is objectively defined, and the user's
intention doesn't come into it. The mean is not a robust measure of
central tendency, the median is, regardless of why you pick one or the
other.


Okay, I see what you mean. I wasn't thinking of robustness as a
technical term but now I see that you are correct.

Perhaps what I should have said is that whether or not this matters
depends on the problem at hand (hopefully this isn't an important
medical trial) and the particular type of data that you have; assuming
normality is fine in many cases even if the data is not "really"
normal.


"Having outliers" literally means that assuming normality is not fine. If 
assuming normality were fine, then you wouldn't need to remove outliers.


--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco

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When is overriding __getattr__ is useful?

[Rodrick Brown]

Can someone provide an example why one would want to override __getattr__
and __getattribute__ in a class?
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Re: what’s the difference between socket.send() and socket.sendall() ?

[Chris Angelico]

On Tue, Jan 8, 2013 at 2:28 AM, Steven D'Aprano
 wrote:
> I
>   once was on a maths mailing list for about three years before I
>   realised that the most prolific and helpful person there was as
>   blind as a bat.

And that, I think, is what s/he would have most wanted: three years
(more, most likely) without any sort of special treatment. It's all
very well to talk about anti-discrimination laws, but on the internet,
nobody knows you're a bat, if I can mangle that expression without
offending people. We have some excellent people on a couple of MUDs
I'm on who are, similarly, blind and using screen-readers. Again, you
don't even know that that's the case until/unless a question comes out
about some piece of ASCII art (which there's a very VERY little of in
Threshold), or some client-specific question hints at the fact that
s/he is using one of the reader-friendly clients (which are fairly
ugly to the sighted).

As to the use of color for emphasis, though - I don't think the OP
used it like that. I've no idea what the significance of white-on-blue
words was, there; it completely eludes me. Maybe he was sending a
secret message in the color codes? In any case, Steven's eight reasons
are absolutely right; when HTML code isn't adding information, it
should be stripped, and when it is adding information, you risk a
large proportion of people not seeing it. So there's never a good time
to use HTML.

ChrisA
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Vigil, the eternal morally vigilant programming language

[Alain Ketterlin]

I just came across Vigil, an extension to python for serious software
engineers, at https://github.com/munificent/vigil and thought everybody
in this group would be interested (sorry if it has been announced
before).

>From README:

| Vigil is a very safe programming language, and an entry in the January
| 2013 PLT Games competition.
| 
| Many programming languages claim to take testing, contracts and safety
| seriously, but only Vigil is truly vigilant about not allowing code
| that fails to pass programmatic specifications.

Enjoy.

-- Alain.
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Re: Vigil, the eternal morally vigilant programming language

[Chris Angelico]

On Tue, Jan 8, 2013 at 3:01 AM, Alain Ketterlin
 wrote:
>
> I just came across Vigil, an extension to python for serious software
> engineers, at https://github.com/munificent/vigil and thought everybody
> in this group would be interested (sorry if it has been announced
> before).

It's the logical derivation of the principle that every program, once
written, could be shortened by at least one instruction and contains
at least one bug. From that, you can deduce that every program can be
logically reduced to a single instruction that doesn't work.

Vigil assists you with this logical reduction.

ChrisA
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Re: problem with exam task for college

[jeltedeproft]

ok after another round of reparations, my update works again and it updates the 
fuel meter, but i still can't get the view of the spaceship to rotate, for now 
only the direction the spaceship accelerates when pressing "up" changes after a 
rotation, but the spaceship itself keeps pointing up. This is the code for the 
rotating :p.s : the problem has to be in this code because the update of 
the view of the position of the spaceship does work.


def update(self,dt):
self.velocity = self.velocity + (self.acceleration * dt)
self.pos = self.pos + self.velocity * dt
a = 0
b = 0
if scene.kb.keys:
a = a + 0.001 
s = scene.kb.getkey()
if (s == "up"):
if self.zicht.meter.height != 0:
self.velocity = self.velocity + self.gas
self.vlam.visible = True
b = b + 2
self.zicht.meter.height = self.zicht.meter.height - 0.1
self.zicht.update
if (s == "left"):
self.gas = rotate(self.gas,angle = math.pi/10, axis = (0,0,1))
(x,y,z) = self.frame.axis
self.frame.axis = (x,y,z-0.1)
if (s == "right") :
self.gas = rotate(self.gas,angle = -(math.pi/10), axis = 
(0,0,1))
(x,y,z) = self.frame.axis
self.frame.axis = (x,y,z+0.1)
if (a == 0):
self.vlam.visible = False
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Re: How to modify this script?

[Kurt Hansen]

Den 06/01/13 16.12, chaouche yacine skrev:

I'm not confident this would run on gedit. It works on a python
interpreter if you have a file named data.txt in the same directory
containing your sample data.

It surely has to do with how gedit works then, because the "$" sign
isn't used in python, this business should be a gedit convention. And
sorry, I can't help on that, I'm not a user of gedit myself. Fortunately
others have answered and I beleive one of the solutions worked for you.


It does not seem to be the case :-(

Thank you for trying to help.



*From:* Kurt Hansen 
*To:* python-list@python.org
*Sent:* Sunday, January 6, 2013 3:21 PM
*Subject:* Re: How to modify this script?

Den 06/01/13 15.01, chaouche yacine wrote:
 > Well, I'm not answering your question since I am rewriting the script,
 > because I prefer it this way :)
 >
 > def addline(line):
 >  return "%s\n" % line
[cut]

I surpose I shall put your code between $< and >?

 > printed
 >
 >  >>> 
 > Price table
 > 1  Green apple  $1
 > 5  Green apples  $4
 > 10  Green apples  $7
 > 
 >  >>>

Aha, so you tested it yourself?

When running this in Gedit on four lines of tab-separated text the
output is:

%s\n" % line

def addcolumn(item,nb_columns):
 if nb_columns != 3:
 return "%s" % (3 - nb_columns + 1, item)
 return "%s" % item

output = "\n"
for line in file("data.txt"):
 items = line.strip().split("\t")
 columns = ""
 for item in items :
 columns += addcolumn(item,len(items))
 output  += addline(columns)


output += ""
print output
 >
-- Venlig hilsen
Kurt Hansen
-- http://mail.python.org/mailman/listinfo/python-list





--
Venlig hilsen
Kurt Hansen
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Re: When is overriding __getattr__ is useful?

[Albert Hopkins]

On Mon, Jan 7, 2013, at 10:54 AM, Rodrick Brown wrote:
> Can someone provide an example why one would want to override __getattr__
> and __getattribute__ in a class?


They're good for cases when you want to provide an "attribute-like"
quality but you don't know the attribute in advance.

For example, the xmlrpclib uses __getattr__ to "expose" XML-RPC methods
over the wire when it doesn't necessarily know what methods are exposed
by the service.  This allows you do simply do

>>> service.method(*args)

And have the method "seem" like it's just a local method on an object.


There are countless other examples.  But that's just one that can be
found in the standard library.

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Re: problem with exam task for college

[Vincent Vande Vyvre]

Le 07/01/13 17:22, jeltedepr...@hotmail.com a écrit :
> ok after another round of reparations, my update works again and it updates 
> the fuel meter, but i still can't get the view of the spaceship to rotate, 
> for now only the direction the spaceship accelerates when pressing "up" 
> changes after a rotation, but the spaceship itself keeps pointing up. This is 
> the code for the rotating :p.s : the problem has to be in this code 
> because the update of the view of the position of the spaceship does work.
>
>
> def update(self,dt):
> self.velocity = self.velocity + (self.acceleration * dt)
> self.pos = self.pos + self.velocity * dt
> a = 0
> b = 0
> if scene.kb.keys:
> a = a + 0.001 
> s = scene.kb.getkey()
> if (s == "up"):
> if self.zicht.meter.height != 0:
> self.velocity = self.velocity + self.gas
> self.vlam.visible = True
> b = b + 2
> self.zicht.meter.height = self.zicht.meter.height - 0.1
> self.zicht.update
> if (s == "left"):
> self.gas = rotate(self.gas,angle = math.pi/10, axis = (0,0,1))
> (x,y,z) = self.frame.axis
> self.frame.axis = (x,y,z-0.1)
> if (s == "right") :
> self.gas = rotate(self.gas,angle = -(math.pi/10), axis = 
> (0,0,1))
> (x,y,z) = self.frame.axis
> self.frame.axis = (x,y,z+0.1)
> if (a == 0):
> self.vlam.visible = False
Are you sure with this code:

(x,y,z) = self.frame.axis ?

frame.axis is a 'cvisual.vector' and this unpacking cause a program
crashes with a segfault.

For left-rigth moves of the LEM, this code seems works:

--

if scene.kb.keys:
key = scene.kb.getkey()
if key == "left":
# Set left deviation
self.frame.axis -= (0, 0, 0.05)
self.gas = vector(-sin(self.angle), cos(self.angle))

elif key == "right":
# Set right deviation
self.frame.axis += (0, 0, 0.05)
self.gas = vector(sin(self.angle), cos(self.angle))

elif key == "up":
self.deviate()

def deviate(self):
# Set modified velocity
self.frame.velocity += self.gas
self.frame.pos += self.frame.velocity
# Reset falling velocity
self.frame.velocity -= self.gas

--

with angle = PI / 2.0

-- 
Vincent V.V.
Oqapy  . Qarte
 . PaQager 
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help

[kwakukwatiah]

download wxpython but whenever I try to use it I get this I’m a beginner in 
python pls I need help.
Traceback (most recent call last):
  File "C:/Python27/wxp.py", line 1, in 
import wx
  File "C:\Python27\lib\site-packages\wx-2.8-msw-unicode\wx\__init__.py", line 
45, in 
from wx._core import *
  File "C:\Python27\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py", line 4, 
in 
import _core_
ImportError: DLL load failed: %1 is not a valid Win32 application.-- 
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Re: How to modify this script?

[Gertjan Klein]

Kurt Hansen wrote:


To convert tab-separated text lines into a HTML-table:


As you apparently didn't receive answers that worked for you I tried to 
get what you want to work and test it in Gedit. Here's the result:


$<
lines = $GEDIT_SELECTED_TEXT.split("\n");
output = '\n';

max_columns = 0
for line in lines:
col_count = len(line.split("\t"))
if col_count \> max_columns:
max_columns = col_count

for line in lines:
if line == '':
continue

output += '';

columns = line.split("\t");
if len(columns) == 1:
output += ('' % max_columns) + line + 
'\n'

continue

for item in columns:
output += '' + item + ''

output += '\n';

output += '';
return output
>

(Watch out for line wraps! I don't know how to stop Thunderbird from 
inserting them.)


It really isn't all that difficult. The code determines the (maximum) 
number of columns present. It then processes each line; if one is found 
with exactly one column (i.e., no tabs), it applies a colspan equal to 
the maximum number of columns. This works for your test and similar data.


As I said, this is copy/pasted from a working Gedit snippet. If it works 
for you, I'd try experimenting a bit -- what should happen when the 
number of columns is larger than 1 but less than the maximum? 
Programming isn't magic. You might start enjoying it.


HTH,
Gertjan.


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[Offtopic] Line fitting [was Re: Numpy outlier removal]

[Steven D'Aprano]

On Mon, 07 Jan 2013 15:20:57 +, Oscar Benjamin wrote:

> There are sometimes good reasons to get a line of best fit by eye. In
> particular if your data contains clusters that are hard to separate,
> sometimes it's useful to just pick out roughly where you think a line
> through a subset of the data is.

Cherry picking subsets of your data as well as line fitting by eye? Two 
wrongs do not make a right.

If you're going to just invent a line based on where you think it should 
be, what do you need the data for? Just declare "this is the line I wish 
to believe in" and save yourself the time and energy of collecting the 
data in the first place. Your conclusion will be no less valid.

How do you distinguish between "data contains clusters that are hard to 
separate" from "data doesn't fit a line at all"?

Even if the data actually is linear, on what basis could we distinguish 
between the line you fit by eye (say) y = 2.5x + 3.7, and the line I fit 
by eye (say) y = 3.1x + 4.1? The line you assert on the basis of purely 
subjective judgement can be equally denied on the basis of subjective 
judgement.

Anyone can fool themselves into placing a line through a subset of non-
linear data. Or, sadly more often, *deliberately* cherry picking fake 
clusters in order to fool others. Here is a real world example of what 
happens when people pick out the data clusters that they like based on 
visual inspection:

http://www.skepticalscience.com/images/TempEscalator.gif

And not linear by any means, but related to the cherry picking theme:

http://www.skepticalscience.com/pics/1_ArcticEscalator2012.gif


To put it another way, when we fit patterns to data by eye, we can easily 
fool ourselves into seeing patterns that aren't there, or missing the 
patterns which are there. At best line fitting by eye is prone to honest 
errors; at worst, it is open to the most deliberate abuse. We have eyes 
and brains that evolved to spot the ripe fruit in trees, not to spot 
linear trends in noisy data, and fitting by eye is not safe or 
appropriate.


-- 
Steven
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test failed: test_urlwithfrag

[Elli Lola]

Dear python team,I never used python before and installed it today the first time, so I have no idea what to do about this failure:$ ./python -m test -v test_urlwithfrag== CPython 3.3.0 (default, Jan 4 2013, 23:08:00) [GCC 4.6.3]==   Linux-3.2.0-35-generic-pae-i686-with-debian-wheezy-sid little-endian==   /home/me/Programme/Python/Python-3.3.0/build/test_python_30744Testing
 with flags: sys.flags(debug=0, inspect=0, interactive=0, optimize=0, 
dont_write_bytecode=0, no_user_site=0, no_site=0, ignore_environment=0, 
verbose=0, bytes_warning=0, quiet=0, hash_randomization=1)[1/1] test_urlwithfragtest test_urlwithfrag crashed -- Traceback (most recent call last):  File "/home/me/Programme/Python/Python-3.3.0/Lib/test/regrtest.py", line 1213, in runtest_inner    the_package = __import__(abstest, globals(), locals(), [])ImportError: No module named 'test.test_urlwithfrag'1 test failed:    test_urlwithfragIf you need more information, please tell me. It would be very great if you could help me. Thank you in advance.Elli Meisner
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OT: local technical community portals

[Jason Hsu]

For the Minneapolis/St. Paul area of Minnesota, there is a technical community 
portal at http://tech.mn/.  You'll see that this portal has links to user 
groups, networking events, jobs, etc.  No, I didn't start this thread to tout 
this site.

MY QUESTION: What are the local technical community portals for other places, 
such as Chicago, Silicon Valley, Los Angeles, San Diego, Dallas, Atlanta, 
Boston, etc.?
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I'm looking for a Junior level Django job (telecommute)

[P Dev]

I'm looking for a Junior level Django job (telecommute)

About me:

- less than year of experience with Python/Django

- Intermediate knowledge of Python/Django
- Experience with Linux
- Experience with Django ORM
- Passion for developing high-quality software and Python language

- I am able to use many aplications, for example (south, mptt, 
django-debug-toolbar etc.)

- English: communicative, still learning

I would like to develop my qualifications

I can be reached anytime via email at dreampr...@gmail.com

Thank you.   
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Re: help

[Chris Angelico]

On Tue, Jan 8, 2013 at 10:35 AM,   wrote:
> download wxpython but whenever I try to use it I get this I’m a beginner in
> python pls I need help.
>
> ImportError: DLL load failed: %1 is not a valid Win32 application.

Did you download the 64-bit version on a 32-bit system?

Chris Angelico
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Re: [Offtopic] Line fitting [was Re: Numpy outlier removal]

[Chris Angelico]

On Tue, Jan 8, 2013 at 4:58 AM, Steven D'Aprano
 wrote:
> Anyone can fool themselves into placing a line through a subset of non-
> linear data. Or, sadly more often, *deliberately* cherry picking fake
> clusters in order to fool others. Here is a real world example of what
> happens when people pick out the data clusters that they like based on
> visual inspection:
>
> http://www.skepticalscience.com/images/TempEscalator.gif

And sensible people will notice that, even drawn like that, it's only
a ~0.6 deg increase across ~30 years. Hardly statistically
significant, given that weather patterns have been known to follow
cycles at least that long. But that's nothing to do with drawing lines
through points, and more to do with how much data you collect before
you announce a conclusion, and how easily a graph can prove any point
you like.

Statistical analysis is a huge science. So is lying. And I'm not sure
most people can pick one from the other.

ChrisA
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INSTRUCTOR SOLUTIONS MANUAL :: Engineering Vibration 3rd Ed by Inman

[kalvinmanual]

I have solutions manuals to all problems and exercises in these textbooks. To 
get one in an electronic format contact me at: kalvinmanual(at)gmail(dot)com 
and let me know its title, author and edition. Please this service is NOT free.


INSTRUCTOR SOLUTIONS MANUAL :: Linear Algebra and Its Applications 3rd ed by 
David C. Lay
INSTRUCTOR SOLUTIONS MANUAL :: Linear Algebra Done Right, 2nd Ed by Sheldon 
Axler
INSTRUCTOR SOLUTIONS MANUAL :: Linear Algebra with Applications (6th Ed., S. 
Leon)
INSTRUCTOR SOLUTIONS MANUAL :: Linear Algebra with Applications 3rd Ed by Otto 
Bretscher
INSTRUCTOR SOLUTIONS MANUAL :: Linear Algebra With Applications, 2nd Edition by 
W. Keith Nicholson
INSTRUCTOR SOLUTIONS MANUAL :: Linear Circuit Analysis Time Domain, Phasor and 
Laplace.., 2nd Ed, Lin
INSTRUCTOR SOLUTIONS MANUAL :: Linear Circuit Analysis, 2nd Ed by DeCarlo , 
Pen-Min Lin
INSTRUCTOR SOLUTIONS MANUAL :: Linear dynamic systems and signals by Zoran Gajic
INSTRUCTOR SOLUTIONS MANUAL :: Linear Systems And Signals, 1stE, B P Lathi
INSTRUCTOR SOLUTIONS MANUAL :: Machine Design : An Integrated Approach (3rd 
Ed., Norton)
INSTRUCTOR SOLUTIONS MANUAL :: Machines and Mechanisms - Applied Kinematic 
Analysis, 3E by David H. Myszka
INSTRUCTOR SOLUTIONS MANUAL :: Managerial Accounting 11th Ed by Garrison & 
Noreen
INSTRUCTOR SOLUTIONS MANUAL :: Managerial Accounting 13th E by Garrison, 
Noreen, Brewer
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INSTRUC

Searching through two logfiles in parallel?

[Victor Hooi]

Hi,

I'm trying to compare two logfiles in Python.

One logfile will have lines recording the message being sent:

05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9

the other logfile has line recording the message being received

05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9

The goal is to compare the time stamp between the two - we can safely assume 
the timestamp on the message being received is later than the timestamp on 
transmission.

If it was a direct line-by-line, I could probably use itertools.izip(), right?

However, it's not a direct line-by-line comparison of the two files - the lines 
I'm looking for are interspersed among other loglines, and the time difference 
between sending/receiving is quite variable.

So the idea is to iterate through the sending logfile - then iterate through 
the receiving logfile from that timestamp forwards, looking for the matching 
pair. Obviously I want to minimise the amount of back-forth through the file.

Also, there is a chance that certain messages could get lost - so I assume 
there's a threshold after which I want to give up searching for the matching 
received message, and then just try to resync to the next sent message.

Is there a Pythonic way, or some kind of idiom that I can use to approach this 
problem?

Cheers,
Victor
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Re: [Offtopic] Line fitting [was Re: Numpy outlier removal]

[Oscar Benjamin]

On 7 January 2013 17:58, Steven D'Aprano
 wrote:
> On Mon, 07 Jan 2013 15:20:57 +, Oscar Benjamin wrote:
>
>> There are sometimes good reasons to get a line of best fit by eye. In
>> particular if your data contains clusters that are hard to separate,
>> sometimes it's useful to just pick out roughly where you think a line
>> through a subset of the data is.
>
> Cherry picking subsets of your data as well as line fitting by eye? Two
> wrongs do not make a right.

It depends on what you're doing, though. I wouldn't use an eyeball fit
to get numbers that were an important part of the conclusion of some
or other study. I would very often use it while I'm just in the
process of trying to understand something.

> If you're going to just invent a line based on where you think it should
> be, what do you need the data for? Just declare "this is the line I wish
> to believe in" and save yourself the time and energy of collecting the
> data in the first place. Your conclusion will be no less valid.

An example: Earlier today I was looking at some experimental data. A
simple model of the process underlying the experiment suggests that
two variables x and y will vary in direct proportion to one another
and the data broadly reflects this. However, at this stage there is
some non-normal variability in the data, caused by experimental
difficulties. A subset of the data appears to closely follow a well
defined linear pattern but there are outliers and the pattern breaks
down in an asymmetric way at larger x and y values. At some later time
either the sources of experimental variation will be reduced, or they
will be better understood but for now it is still useful to estimate
the constant of proportionality in order to check whether it seems
consistent with the observed values of z. With this particular dataset
I would have wasted a lot of time if I had tried to find a
computational method to match the line that to me was very visible so
I chose the line visually.

>
> How do you distinguish between "data contains clusters that are hard to
> separate" from "data doesn't fit a line at all"?
>

In the example I gave it isn't possible to make that distinction with
the currently available data. That doesn't make it meaningless to try
and estimate the parameters of the relationship between the variables
using the preliminary data.

> Even if the data actually is linear, on what basis could we distinguish
> between the line you fit by eye (say) y = 2.5x + 3.7, and the line I fit
> by eye (say) y = 3.1x + 4.1? The line you assert on the basis of purely
> subjective judgement can be equally denied on the basis of subjective
> judgement.

It gets a bit easier if the line is constrained to go through the
origin. You seem to be thinking that the important thing is proving
that the line is "real", rather than identifying where it is. Both
things are important but not necessarily in the same problem. In my
example, the "real line" may not be straight and may not go through
the origin, but it is definitely there and if there were no
experimental problems then the data would all be very close to it.

> Anyone can fool themselves into placing a line through a subset of non-
> linear data. Or, sadly more often, *deliberately* cherry picking fake
> clusters in order to fool others. Here is a real world example of what
> happens when people pick out the data clusters that they like based on
> visual inspection:
>
> http://www.skepticalscience.com/images/TempEscalator.gif
>
> And not linear by any means, but related to the cherry picking theme:
>
> http://www.skepticalscience.com/pics/1_ArcticEscalator2012.gif
>
>
> To put it another way, when we fit patterns to data by eye, we can easily
> fool ourselves into seeing patterns that aren't there, or missing the
> patterns which are there. At best line fitting by eye is prone to honest
> errors; at worst, it is open to the most deliberate abuse. We have eyes
> and brains that evolved to spot the ripe fruit in trees, not to spot
> linear trends in noisy data, and fitting by eye is not safe or
> appropriate.

This is all true. But the human brain is also in many ways much better
than a typical computer program at recognising patterns in data when
the data can be depicted visually. I would very rarely attempt to
analyse data without representing it in some visual form. I also think
it would be highly foolish to go so far with refusing to eyeball data
that you would accept the output of some regression algorithm even
when it clearly looks wrong.


Oscar
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Re: Searching through two logfiles in parallel?

[Oscar Benjamin]

On 7 January 2013 22:10, Victor Hooi  wrote:
> Hi,
>
> I'm trying to compare two logfiles in Python.
>
> One logfile will have lines recording the message being sent:
>
> 05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9
>
> the other logfile has line recording the message being received
>
> 05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9
>
> The goal is to compare the time stamp between the two - we can safely assume 
> the timestamp on the message being received is later than the timestamp on 
> transmission.
>
> If it was a direct line-by-line, I could probably use itertools.izip(), right?
>
> However, it's not a direct line-by-line comparison of the two files - the 
> lines I'm looking for are interspersed among other loglines, and the time 
> difference between sending/receiving is quite variable.
>
> So the idea is to iterate through the sending logfile - then iterate through 
> the receiving logfile from that timestamp forwards, looking for the matching 
> pair. Obviously I want to minimise the amount of back-forth through the file.
>
> Also, there is a chance that certain messages could get lost - so I assume 
> there's a threshold after which I want to give up searching for the matching 
> received message, and then just try to resync to the next sent message.
>
> Is there a Pythonic way, or some kind of idiom that I can use to approach 
> this problem?

Assuming that you can impose a maximum time between the send and
recieve timestamps, something like the following might work
(untested):

def find_matching(logfile1, logfile2, maxdelta):
buf = {}
logfile2 = iter(logfile2)
for msg1 in logfile1:
if msg1.key in buf:
yield msg1, buf.pop(msg1.key)
continue
maxtime = msg1.time + maxdelta
for msg2 in logfile2:
if msg2.key == msg1.key:
yield msg1, msg2
break
buf[msg2.key] = msg2
if msg2.time > maxtime:
break
else:
yield msg1, 'No match'


Oscar
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Re: help

[Ian Kelly]

On Mon, Jan 7, 2013 at 12:37 PM, Chris Angelico  wrote:
> On Tue, Jan 8, 2013 at 10:35 AM,   wrote:
>> download wxpython but whenever I try to use it I get this I’m a beginner in
>> python pls I need help.
>>
>> ImportError: DLL load failed: %1 is not a valid Win32 application.
>
> Did you download the 64-bit version on a 32-bit system?

Or perhaps a 32-bit wxPython version with a 64-bit Python installation?
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Re: test failed: test_urlwithfrag

[Irmen de Jong]

On 7-1-2013 19:26, Elli Lola wrote:
> I never used python before and installed it today the first time, so I have 
> no idea what
> to do about this failure:
> 
> 
> $ ./python -m test -v test_urlwithfrag

[..snip..]

> ImportError: No module named 'test.test_urlwithfrag'
> 
> 1 test failed:
> test_urlwithfrag

The error message says it all, really: there is no regression test module called
"test_urlwithfrag".  (At least, not on my python 3.3 installation)

Check the contents of your /Lib/test directory to see what 
is
available instead.


Irmen

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Re: Searching through two logfiles in parallel?

[Victor Hooi]

Hi Oscar,

Thanks for the quick reply =).

I'm trying to understand your code properly, and it seems like for each line in 
logfile1, we loop through all of logfile2?

The idea was that it would remember it's position in logfile2 as well - since 
we can assume that the loglines are in chronological order - we only need to 
search forwards in logfile2 each time, not from the beginning each time.

So for example - logfile1:

05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9 
05:00:08 Message sent - Value A: 3.3, Value B: 4.3, Value C: 2.3
05:00:14 Message sent - Value A: 1.0, Value B: 0.4, Value C: 5.4

logfile2:

05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9 
05:00:12 Message received - Value A: 3.3, Value B: 4.3, Value C: 2.3
05:00:15 Message received - Value A: 1.0, Value B: 0.4, Value C: 5.4

The idea is that I'd iterate through logfile 1 - I'd get the 05:00:06 logline - 
I'd search through logfile2 and find the 05:00:09 logline.

Then, back in logline1 I'd find the next logline at 05:00:08. Then in logfile2, 
instead of searching back from the beginning, I'd start from the next line, 
which happens to be 5:00:12.

In reality, I'd need to handle missing messages in logfile2, but that's the 
general idea.

Does that make sense? (There's also a chance I've misunderstood your buf code, 
and it does do this - in that case, I apologies - is there any chance you could 
explain it please?)

Cheers,
Victor

On Tuesday, 8 January 2013 09:58:36 UTC+11, Oscar Benjamin  wrote:
> On 7 January 2013 22:10, Victor Hooi  wrote:
> 
> > Hi,
> 
> >
> 
> > I'm trying to compare two logfiles in Python.
> 
> >
> 
> > One logfile will have lines recording the message being sent:
> 
> >
> 
> > 05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9
> 
> >
> 
> > the other logfile has line recording the message being received
> 
> >
> 
> > 05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9
> 
> >
> 
> > The goal is to compare the time stamp between the two - we can safely 
> > assume the timestamp on the message being received is later than the 
> > timestamp on transmission.
> 
> >
> 
> > If it was a direct line-by-line, I could probably use itertools.izip(), 
> > right?
> 
> >
> 
> > However, it's not a direct line-by-line comparison of the two files - the 
> > lines I'm looking for are interspersed among other loglines, and the time 
> > difference between sending/receiving is quite variable.
> 
> >
> 
> > So the idea is to iterate through the sending logfile - then iterate 
> > through the receiving logfile from that timestamp forwards, looking for the 
> > matching pair. Obviously I want to minimise the amount of back-forth 
> > through the file.
> 
> >
> 
> > Also, there is a chance that certain messages could get lost - so I assume 
> > there's a threshold after which I want to give up searching for the 
> > matching received message, and then just try to resync to the next sent 
> > message.
> 
> >
> 
> > Is there a Pythonic way, or some kind of idiom that I can use to approach 
> > this problem?
> 
> 
> 
> Assuming that you can impose a maximum time between the send and
> 
> recieve timestamps, something like the following might work
> 
> (untested):
> 
> 
> 
> def find_matching(logfile1, logfile2, maxdelta):
> 
> buf = {}
> 
> logfile2 = iter(logfile2)
> 
> for msg1 in logfile1:
> 
> if msg1.key in buf:
> 
> yield msg1, buf.pop(msg1.key)
> 
> continue
> 
> maxtime = msg1.time + maxdelta
> 
> for msg2 in logfile2:
> 
> if msg2.key == msg1.key:
> 
> yield msg1, msg2
> 
> break
> 
> buf[msg2.key] = msg2
> 
> if msg2.time > maxtime:
> 
> break
> 
> else:
> 
> yield msg1, 'No match'
> 
> 
> 
> 
> 
> Oscar
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Re: Searching through two logfiles in parallel?

[Oscar Benjamin]

On 7 January 2013 23:41, Victor Hooi  wrote:
> Hi Oscar,
>
> Thanks for the quick reply =).
>
> I'm trying to understand your code properly, and it seems like for each line 
> in logfile1, we loop through all of logfile2?

No we don't. It iterates once through both files but keeps a buffer of
lines that are within maxdelta time of the current message.

The important line is the line that calls iter(logfile2). Since
logfile2 is replaced by an iterator when we break out of the inner for
loop and then re-enter our place in the iterator is saved. If you can
follow the interactive session below it should make sense:

>>> a = [1,2,3,4,5]
>>> for x in a:
...print x,
...
1 2 3 4 5
>>> for x in a:
...print x,
...
1 2 3 4 5
>>> it = iter(a)
>>> next(it)
1
>>> for x in it:
... print x,
...
2 3 4 5
>>> next(it)
Traceback (most recent call last):
  File "", line 1, in 
StopIteration
>>> for x in it:
... print x,
...
>>> it = iter(a)
>>> for x in it:
... print x,
... if x == 2: break
...
1 2
>>> for x in it:
... print x,
...
3 4 5


I'll repeat the code (with a slight fix):


def find_matching(logfile1, logfile2, maxdelta):
buf = {}
logfile2 = iter(logfile2)
for msg1 in logfile1:
if msg1.key in buf:
yield msg1, buf.pop(msg1.key)
continue
maxtime = msg1.time + maxdelta
for msg2 in logfile2:
if msg2.key == msg1.key:
yield msg1, msg2
break
buf[msg2.key] = msg2
if msg2.time > maxtime:
   yield msg1, 'No match'
   break
else:
yield msg1, 'No match'


Oscar


>
> The idea was that it would remember it's position in logfile2 as well - since 
> we can assume that the loglines are in chronological order - we only need to 
> search forwards in logfile2 each time, not from the beginning each time.
>
> So for example - logfile1:
>
> 05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9
> 05:00:08 Message sent - Value A: 3.3, Value B: 4.3, Value C: 2.3
> 05:00:14 Message sent - Value A: 1.0, Value B: 0.4, Value C: 5.4
>
> logfile2:
>
> 05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9
> 05:00:12 Message received - Value A: 3.3, Value B: 4.3, Value C: 2.3
> 05:00:15 Message received - Value A: 1.0, Value B: 0.4, Value C: 5.4
>
> The idea is that I'd iterate through logfile 1 - I'd get the 05:00:06 logline 
> - I'd search through logfile2 and find the 05:00:09 logline.
>
> Then, back in logline1 I'd find the next logline at 05:00:08. Then in 
> logfile2, instead of searching back from the beginning, I'd start from the 
> next line, which happens to be 5:00:12.
>
> In reality, I'd need to handle missing messages in logfile2, but that's the 
> general idea.
>
> Does that make sense? (There's also a chance I've misunderstood your buf 
> code, and it does do this - in that case, I apologies - is there any chance 
> you could explain it please?)
>
> Cheers,
> Victor
>
> On Tuesday, 8 January 2013 09:58:36 UTC+11, Oscar Benjamin  wrote:
>> On 7 January 2013 22:10, Victor Hooi  wrote:
>>
>> > Hi,
>>
>> >
>>
>> > I'm trying to compare two logfiles in Python.
>>
>> >
>>
>> > One logfile will have lines recording the message being sent:
>>
>> >
>>
>> > 05:00:06 Message sent - Value A: 5.6, Value B: 6.2, Value C: 9.9
>>
>> >
>>
>> > the other logfile has line recording the message being received
>>
>> >
>>
>> > 05:00:09 Message received - Value A: 5.6, Value B: 6.2, Value C: 9.9
>>
>> >
>>
>> > The goal is to compare the time stamp between the two - we can safely 
>> > assume the timestamp on the message being received is later than the 
>> > timestamp on transmission.
>>
>> >
>>
>> > If it was a direct line-by-line, I could probably use itertools.izip(), 
>> > right?
>>
>> >
>>
>> > However, it's not a direct line-by-line comparison of the two files - the 
>> > lines I'm looking for are interspersed among other loglines, and the time 
>> > difference between sending/receiving is quite variable.
>>
>> >
>>
>> > So the idea is to iterate through the sending logfile - then iterate 
>> > through the receiving logfile from that timestamp forwards, looking for 
>> > the matching pair. Obviously I want to minimise the amount of back-forth 
>> > through the file.
>>
>> >
>>
>> > Also, there is a chance that certain messages could get lost - so I assume 
>> > there's a threshold after which I want to give up searching for the 
>> > matching received message, and then just try to resync to the next sent 
>> > message.
>>
>> >
>>
>> > Is there a Pythonic way, or some kind of idiom that I can use to approach 
>> > this problem?
>>
>>
>>
>> Assuming that you can impose a maximum time between the send and
>>
>> recieve timestamps, something like the following might work
>>
>> (untested):
>>
>>
>>
>> def find_matching(logfile1, logfile2, maxdelta):
>>
>> buf = {}
>>
>> logfile2 = iter(logfile2)

Calculate Big Number

[Nac Temha]

Hello,
How to *quickly* calculate large numbers. For example
>>> (10**25) * (2**50)
11258999068426240L




Regards.
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How to implement mouse gesture by python or pyqt ?

[iMath]

It would be better to give me some examples .thanks in advance !

P.S. which module or lib are needed ?
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Re: Calculate Big Number

[Oscar Benjamin]

On 8 January 2013 00:44, Nac Temha  wrote:
> Hello,
> How to quickly calculate large numbers. For example
 (10**25) * (2**50)
> 11258999068426240L

I just tested that line in the interpreter and it ran so quickly it
seemed instantaneous (maybe my computer is faster than yours).

Perhaps you could provide more of an explanation about what isn't fast
enough and why?


Oscar
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INSTRUCTOR SOLUTIONS MANUAL :: Classical Electrodynamics 2nd edition by John David Jackson

[kalvinmanual]

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Thermodynamics, 4th Ed by Sandler
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INSTRUCTOR SOLUTIONS MANUAL :: Chemistry, 10th Ed by Chang
INSTRUCTOR SOLUTIONS MANUAL :: Chip Design for Submicron VLSI CMOS Layout and 
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Solution Guide Version 2.0
INSTRUCTOR SOLUTIONS MANUAL :: Classical Dynamics of Particles and Systems, 5th 
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INSTRUCTOR SOLUTIONS MANUAL :: Classical Dynamics, A Contemporary Approach 
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INSTRUCTOR SOLUTIONS MANUAL :: Classical Electrodynamics 2nd edition by John 
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INSTRUCTOR SOLUTIONS MANUAL :: Classical Electrodynamics by John David Jackson
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INSTRUCTOR SOLUTIONS MANUAL :: Classical Mechanics 2nd Ed by Goldstein
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INSTRUCTOR SOLUTIONS MANUAL :: Communication Networks, 2e, Alberto Leon-G

Re: Ubuntu Python -dbg packages

[Lee Harr]

>> Ok, so now I tried python3.3-dbg but I don't think the pyqt
>> modules are compiled for 3.3 and that may be preventing
>> the import there.
>>
>> Those extension modules would need to be compiled for
>> an exactly matching python interpreter, right?
>
> For Windows visual C compiler, that is true. I do not know about gcc on 
> *nix. I have gotten the impression that it is not necessarily so, except 
> as the C api has changed in a way that affects the extension library. 
> (Given that 3.3 is 3 months old, after 6 months of alpha/beta releases, 
> and has some major improvements, it is past time for libraries that need 
> recompiling to be so.)


Well... lets just say that with the ubuntu python3.3 package it doesn't work:


$ python3.3
Python 3.3.0 (default, Sep 29 2012, 17:17:45) 
[GCC 4.7.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import PyQt4
>>> import PyQt4.QtCore
Traceback (most recent call last):
  File "", line 1, in 
ImportError: No module named 'PyQt4.QtCore'


[plus a whole other problem...]

Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 64, in 
apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 4, in 
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in 
    import apport.fileutils
  File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in 

    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 20, in 

    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 21, in 
    import apt_pkg
ImportError: No module named 'apt_pkg'

Original exception was:
Traceback (most recent call last):
  File "", line 1, in 
ImportError: No module named 'PyQt4.QtCore'




>> So, python3-dbg _should_ be able to import this?
>
> Given that python3 and python3-dbg import the same PyQt4 file, and that 
> you spell PyQt4.QtCore the same (I checked), I am as surprised as you. 

Ok. I will file a Ubuntu bug report.



> >>> import test.test_imp as t; t.test_main()

This does not work for me:

$ python3
Python 3.2.3 (default, Oct 19 2012, 19:53:57) 
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import test
>>> test.test_imp
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: 'module' object has no attribute 'test_imp'


$ python3.3
Python 3.3.0 (default, Sep 29 2012, 17:17:45) 
[GCC 4.7.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import test
>>> test.test_imp
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: 'module' object has no attribute 'test_imp'

[plus that whole Error in sys.excepthook thing too...]


Should this be another bug report for the ubuntu packages?

  
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Difference between these two lists?

[andydtaylor]

Hi,

Python newbie here again - this is probably a quick one. What's the difference 
between the lines I've numbered 1. and 2. below, which produce the following 
results: 

Results:
1. [ANG, BAR, BPK, CTN, QGH, QHD, KXX]
2. ['ANG', 'BAR', 'BPK', 'CTN', 'QGH', 'QHD', 'KXX']

Code:
   cursor_from.execute('SELECT * FROM tubestations LIMIT 1000')
   
   stn_list_short = []
   for row in cursor_from:
  if row[4]:
# Station values for database
stn_list_short.append(row[5])

   1. print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))  
   2. print stn_list_short

Thanks!

Andy
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Re: Difference between these two lists?

[andydtaylor]

I think I can answer my own question on reflection the first one is 
actually  a string I think? I was confused by the square brackets around the 
placeholder %s.
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Re: Calculate Big Number

[Tim Chase]

On 01/07/13 18:44, Nac Temha wrote:

How to *quickly* calculate large numbers. For example

(10**25) * (2**50)

11258999068426240L


that's how...just do the math.  For any other sort of answer, you'd 
have to clarify your question.  On my laptop, that operation came 
back as quickly as I could press 


-tkc





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Re: Difference between these two lists?

[Chris Angelico]

On Tue, Jan 8, 2013 at 12:00 PM,   wrote:
> Hi,
>
> Python newbie here again - this is probably a quick one. What's the 
> difference between the lines I've numbered 1. and 2. below, which produce the 
> following results:
>1. print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))
>2. print stn_list_short

Your first line explicitly joins the strings with commas; the second
implicitly calls repr() on the whole list, which does its best to
produce a valid Python literal. Check out the docs on repr() for the
details on that; you'll see different results depending on the content
of the strings, but at very least they'll always be quoted.

ChrisA
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Re: Difference between these two lists?

[Chris Angelico]

On Tue, Jan 8, 2013 at 12:06 PM,   wrote:
> I think I can answer my own question on reflection the first one is 
> actually  a string I think? I was confused by the square brackets around the 
> placeholder %s.

That's correct. Your first line is putting square brackets around a
comma-joined list of strings; the second gives the representation of a
list. They happen to be superficially similar.

ChrisA
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Re: Calculate Big Number

[Nac Temha]

Thanks for reply. I wonder how quickly calculate big numbers. Can you
explain me as theoretical? Because this numbers overflow size of integer
and double.


On Tue, Jan 8, 2013 at 3:08 AM, Tim Chase wrote:

> On 01/07/13 18:44, Nac Temha wrote:
>
>> How to *quickly* calculate large numbers. For example
>>
>>> (10**25) * (2**50)
>
 112589990684262400**000L
>>
>
> that's how...just do the math.  For any other sort of answer, you'd have
> to clarify your question.  On my laptop, that operation came back as
> quickly as I could press 
>
> -tkc
>
>
>
>
>
>
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Re: Difference between these two lists?

[Roy Smith]

In article <700d2bd9-e1df-4d38-81c7-77029a36c...@googlegroups.com>,
 andydtay...@gmail.com wrote:

> Hi,
> 
> Python newbie here again - this is probably a quick one. What's the 
> difference between the lines I've numbered 1. and 2. below, which produce the 
> following results: 
> 
> Results:
> 1. [ANG, BAR, BPK, CTN, QGH, QHD, KXX]
> 2. ['ANG', 'BAR', 'BPK', 'CTN', 'QGH', 'QHD', 'KXX']
> 
> Code:
>cursor_from.execute('SELECT * FROM tubestations LIMIT 1000')
>
>stn_list_short = []
>for row in cursor_from:
>   if row[4]:
>   # Station values for database
>   stn_list_short.append(row[5])
> 
>1. print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))  
>2. print stn_list_short

Hi Andy,

You should try to reduce this down to some minimal test case.  In this 
case, the database code has nothing to do with it, it's purely a matter 
of how a list of strings is printed.

When you print a list, the repr() of each list element is printed.  The 
repr() of a string includes quotes.  For example:

>>> print str("foo")
foo
>>> print repr("foo")
'foo'

I'm not sure what "map(str, stn_list_short)" is all about.  I'm assuming 
stn_list_short is already a string, so that's a no-op.

In general, the best way to ask about code is to cut-and-paste the exact 
code that you ran.  You didn't run:

>1. print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))  
>2. print stn_list_short

because those are syntax errors.  I understand you were just trying to 
annotate your code to make it easier to explain.  A better way to do 
that would be to comment your code, something like:

>print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))  # line 1
>print stn_list_short  # line 2

Now you've got something which runs, and can be cut-and-pasted 
unmodified into your posting.  That reduces the chance of confusion.
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Re: Difference between these two lists?

[Dave Angel]

On 01/07/2013 08:00 PM, andydtay...@gmail.com wrote:
> Hi,
>
> Python newbie here again - this is probably a quick one. What's the 
> difference between the lines I've numbered 1. and 2. below, which produce the 
> following results: 
>
> Results:
> 1. [ANG, BAR, BPK, CTN, QGH, QHD, KXX]
> 2. ['ANG', 'BAR', 'BPK', 'CTN', 'QGH', 'QHD', 'KXX']
>
> Code:
>cursor_from.execute('SELECT * FROM tubestations LIMIT 1000')
>
>stn_list_short = []
>for row in cursor_from:
>   if row[4]:
>   # Station values for database
>   stn_list_short.append(row[5])
>
>1. print stn_fields = '[%s]' % ', '.join(map(str, stn_list_short))  
>2. print stn_list_short


#2 is easy.  it's just the standard way a list prints itself.  It puts
brackets at begin and end, and then calls repr() on each of the
elements.  Since those elements are str objects, each gets quotes around
it.  Then the list logic adds commas and puts it all together.

In #1, you're doing it by hand.  If you wanted the same result, you'd
have to map the repr, not the str value of each item.

(untested)

.join(map(repr, stn_list_short)



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Re: [Offtopic] Line fitting [was Re: Numpy outlier removal]

[Steven D'Aprano]

On Mon, 07 Jan 2013 22:32:54 +, Oscar Benjamin wrote:

> An example: Earlier today I was looking at some experimental data. A
> simple model of the process underlying the experiment suggests that two
> variables x and y will vary in direct proportion to one another and the
> data broadly reflects this. However, at this stage there is some
> non-normal variability in the data, caused by experimental difficulties.
> A subset of the data appears to closely follow a well defined linear
> pattern but there are outliers and the pattern breaks down in an
> asymmetric way at larger x and y values. At some later time either the
> sources of experimental variation will be reduced, or they will be
> better understood but for now it is still useful to estimate the
> constant of proportionality in order to check whether it seems
> consistent with the observed values of z. With this particular dataset I
> would have wasted a lot of time if I had tried to find a computational
> method to match the line that to me was very visible so I chose the line
> visually.


If you mean:

"I looked at the data, identified that the range a < x < b looks linear 
and the range x > b does not, then used least squares (or some other 
recognised, objective technique for fitting a line) to the data in that 
linear range"

then I'm completely cool with that. That's fine, with the understanding 
that this is the first step in either fixing your measurement problems, 
fixing your model, or at least avoiding extrapolation into the non-linear 
range.

But that is not fitting a line by eye, which is what I am talking about.

If on the other hand you mean:

"I looked at the data, identified that the range a < x < b looked linear, 
so I laid a ruler down over the graph and pushed it around until I was 
satisfied that the ruler looked more or less like it fitted the data 
points, according to my guess of what counts as a close fit"

that *is* fitting a line by eye, and it is entirely subjective and 
extremely dodgy for anything beyond quick and dirty back of the envelope 
calculations[1]. That's okay if all you want is to get something within 
an order of magnitude or so, or a line roughly pointing in the right 
direction, but that's all.


[...]
> I also think it would
> be highly foolish to go so far with refusing to eyeball data that you
> would accept the output of some regression algorithm even when it
> clearly looks wrong.

I never said anything of the sort.

I said, don't fit lines to data by eye. I didn't say not to sanity check 
your straight line fit is reasonable by eyeballing it.



[1] Or if your data is so accurate and noise-free that you hardly have to 
care about errors, since there clearly is one and only one straight line 
that passes through all the points.


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Re: Calculate Big Number

[Tomasz Rola]

On Tue, 8 Jan 2013, Nac Temha wrote:

> Hello,
> How to *quickly* calculate large numbers. For example
> >>> (10**25) * (2**50)
> 11258999068426240L
> 

Um, Karatsuba multiplication?

http://en.wikipedia.org/wiki/Karatsuba_algorithm

Or see what GMP folks are doing:

http://en.wikipedia.org/wiki/GNU_Multi-Precision_Library

Regards,
Tomasz Rola

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** As the answer, master did "rm -rif" on the programmer's home**
** directory. And then the C programmer became enlightened...  **
** **
** Tomasz Rola  mailto:tomasz_r...@bigfoot.com **
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Re: Calculate Big Number

[Dave Angel]

On 01/07/2013 07:44 PM, Nac Temha wrote:
> Hello,
> How to *quickly* calculate large numbers. For example
 (10**25) * (2**50)
> 11258999068426240L
>
>

Since all of the terms are const, you could just use

print "11258999068426240L"

Or if you have some constraints on those numbers, you could preprocess the 
calculation with meatware.

For example, if you wnated   (10**var1) * (var2**var3),  where var1, var2 and 
var3 are  all ints, then you could save some time by doing:
print str(var2**var3)+"0"*var1

Or you could write C code to do multiprecision arithmetic.  Or ...

What are your constraints?  If you have to calculate an arbitrary expression of 
ints and longs, you'll spend a lot more time typing it in than the computer 
will calculating it.

BTW, if you want a non-trivial answer, you should specify what Python version 
you're targeting.   I arbitrarily chose 2.7 for my response.m


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Re: Calculate Big Number

[Dave Angel]

On 01/07/2013 08:22 PM, Nac Temha wrote:
> Thanks for reply. I wonder how quickly calculate big numbers. Can you
> explain me as theoretical? Because this numbers overflow size of integer
> and double.
Please don't top-post.  It makes the context totally out of order.

Python automatically promotes to long when doing integer arithmetic, and
the numbers grow too big.  And on version 3, there's no distinction. 
floats are not used, or there would be errors.

Your "wonder statement" is not complete, so I'm not sure what you're
asking.  Could you elaborate?  Are you asking to see the source code for
the python interpreter that's responsible for this?  Or an algorithm
that it might use?  Are you curious in a language-agnostic way how one
might do multiple-precision arithmetic?  I've written arithmetic
packages in PL/I and in BASIC, plus implemented the microcoded math in
one processor.  So, for example, I might explain how one could compute
X**Y when Y is a positive integer, without doing Y-1 multiplies.



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Re: Calculate Big Number

[Roy Smith]

In article ,
 Nac Temha  wrote:

> Thanks for reply. I wonder how quickly calculate big numbers. Can you
> explain me as theoretical? Because this numbers overflow size of integer
> and double.

Now, that's a good question.  The answer is that Python implements 
multiple-precision arithmetic.  This is an awesome feature, as it means 
you never have to worry about integer overflow again.  A good 
introduction to the subject can be found at

http://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic
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Re: [Offtopic] Line fitting [was Re: Numpy outlier removal]

[Steven D'Aprano]

On Tue, 08 Jan 2013 06:43:46 +1100, Chris Angelico wrote:

> On Tue, Jan 8, 2013 at 4:58 AM, Steven D'Aprano
>  wrote:
>> Anyone can fool themselves into placing a line through a subset of non-
>> linear data. Or, sadly more often, *deliberately* cherry picking fake
>> clusters in order to fool others. Here is a real world example of what
>> happens when people pick out the data clusters that they like based on
>> visual inspection:
>>
>> http://www.skepticalscience.com/images/TempEscalator.gif
> 
> And sensible people will notice that, even drawn like that, it's only a
> ~0.6 deg increase across ~30 years. Hardly statistically significant,

Well, I don't know about "sensible people", but magnitude of an effect 
has little to do with whether or not something is statistically 
significant or not. Given noisy data, statistical significance relates to 
whether or not we can be confident that the effect is *real*, not whether 
it is a big effect or a small effect.

Here's an example: assume that you are on a fixed salary with a constant 
weekly income. If you happen to win the lottery one day, and consequently 
your income for that week quadruples, that is a large effect that fails 
to have any statistical significance -- it's a blip, not part of any long-
term change in income. You can't conclude that you'll win the lottery 
every week from now on.

On the other hand, if the government changes the rules relating to tax, 
deductions, etc., even by a small amount, your weekly income might go 
down, or up, by a single dollar. Even though that is a tiny effect, it is 
*not* a blip, and will be statistically significant. In practice, it 
takes a certain number of data points to reach that confidence level. 
Your accountant, who knows the tax laws, will conclude that the change is 
real immediately, but a statistician who sees only the pay slips may take 
some months before she is convinced that the change is signal rather than 
noise. With only three weeks pay slips in hand, the statistician cannot 
be sure that the difference is not just some accounting error or other 
fluke, but each additional data point increases the confidence that the 
difference is real and not just some temporary aberration.

The other meaning of "significant" has nothing to do with statistics, and 
everything to do with "a difference is only a difference if it makes a 
difference". 0.2° per decade doesn't sound like much, not when we 
consider daily or yearly temperatures that typically have a range of tens 
of degrees between night and day, or winter and summer. But that is 
misunderstanding the nature of long-term climate versus daily weather and 
glossing over the fact that we're only talking about an average and 
ignoring changes to the variability of the climate: a small increase in 
average can lead to a large increase in extreme events.


> given that weather patterns have been known to follow cycles at least
> that long.

That is not a given. "Weather patterns" don't last for thirty years. 
Perhaps you are talking about climate patterns? In which case, well, yes, 
we can see a very strong climate pattern of warming on a time scale of 
decades, with no evidence that it is a cycle.

There are, of course, many climate cycles that take place on a time frame 
of years or decades, such as the North Atlantic Oscillation and the El 
Nino Southern Oscillation. None of them are global, and as far as I know 
none of them are exactly periodic. They are noise in the system, and 
certainly not responsible for linear trends.



-- 
Steven
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Re: Calculate Big Number

[Dave Angel]

(forwarding the private reply to the group)

On 01/07/2013 09:03 PM, Nac Temha wrote:
> Thanks. I using version 2.7 .I want to understand how to handling big
> number. Just  want to know logic.  Without going into further details but I
> want to learn logic of this issue. How to keep datas in python? Using data
> structure? and datas how to handling for calculating?
> 
> 

Since I don't understand your questions, I'll make some guesses.  If
these don't cover it, please reword your questions.

I'll assume you do NOT want internal details of how the python
interpreter manages it.   I'll assume you DO want to know how to write
your python program so that as much accuracy as possible is used in the
calculations.

First comment - as soon as you introduce a floating point (non-integer)
value into the expression, you have the potential of losing precision.
In general, when doing mixed arithmetic, python will convert the result
to float.  Lots can be written (and has been written) about floats,
Decimals, quantization and rounding.  I'm again assuming you're NOT
asking about these.

In Python 2.7, there are two kinds of integers, int and long.  An int is
limited to some processor-specific size, usually 32 or 64 bits.  A long
has no practical limit, though after a few hundred million digits, it
gets pretty memory hungry and piggishly slow.  A long is NOT related to
the C type of the same name.

If you have an integer in your source code that's larger than that
limit, it'll automatically be promoted to long.

If you want to see the type of a particular object, you can use
type(myobj).   For example,

print type(2397493749328734972349873)
will print: 

If you add, subtract, multiply or ** two int objects, and the result is
too big for an int, it'll automatically be promoted to long.

If you divide two integers with /  the result is floored.  Thus the
result is an integer.  That changes in Python 3, where you can get this
result with //.

If you call some library function on a long, it may or may not be able
to handle it, check the docs.  But in your own code, it's pretty easy to
keep things clean.

If you have more questions, please be specific.

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Re: Difference between these two lists?

[andydtaylor]

Thanks, I think I'm clear now. 

I guess (map(str, stn_list)) was all about how to make a string starting with 
integers. I picked that up and began using it without realising it was over 
catering for a list already containing strings, and join(stn_list) was really 
all I required.

Repr and Eval I think I get. Eval certainly. That's a familiar concept, and one 
I hope to use tomorrow to feed a line to psycopg2. 

I might have opened a can of worms on map and repr though... I'll do some more 
reading tomorrow.

Top tip on the code annotation, I didn't really think that through.

Thanks again,

Andy
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Re: Difference between these two lists?

[Chris Angelico]

On Tue, Jan 8, 2013 at 1:21 PM,   wrote:
> Repr and Eval I think I get. Eval certainly. That's a familiar concept, and 
> one I hope to use tomorrow to feed a line to psycopg2.

I hope not. Why do you need eval? It's extremely dangerous.

Chances are there's a better way to do it; if your users are entering
strings like

"['Foo', 'Bar']"

and you want them to be interpreted as lists, then you can get a much
safer function ast.literal_eval - it's equivalent to eval, but (as the
name suggests) works only with literals, so you can't call functions
etc. But even that may be overkill, depending on what you actually
need.

ChrisA
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FYI - wiki.python.org compromised

[Brian Curtin]

On December 28th, an unknown attacker used a previously unknown remote
code exploit on http://wiki.python.org/. The attacker was able to get
shell access as the "moin" user, but no other services were affected.

Some time later, the attacker deleted all files owned by the "moin"
user, including all instance data for both the Python and Jython
wikis. The attack also had full access to all MoinMoin user data on
all wikis. In light of this, the Python Software Foundation encourages
all wiki users to change their password on other sites if the same one
is in use elsewhere. We apologize for the inconvenience and will post
further news as we bring the new and improved wiki.python.org online.

If you have any questions about this incident please contact
jnol...@python.org. Thank you for your patience.
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how to download internet files by python ?

[iMath]

for example ,if I want to download this file ,how to implement the download 
functionality by python ?

http://down.51voa.com/201208/se-ed-foreign-students-friends-16aug12.mp3

as for  download speed ,of course ,the fast ,the better ,so how to implement it 
?

It would be better to show me an example :) thanks !!!
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How to get the selected text of the webpage in chrome through python ?

[iMath]

How to get the selected text of the webpage in chrome through python ?
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Re: how to download internet files by python ?

[Cameron Simpson]

On 07Jan2013 20:19, iMath  wrote:
| for example ,if I want to download this file ,how to implement the download 
functionality by python ?
| 
| http://down.51voa.com/201208/se-ed-foreign-students-friends-16aug12.mp3
| 
| as for  download speed ,of course ,the fast ,the better ,so how to implement 
it ?
| It would be better to show me an example :) thanks !!!

Look at urllib2.
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Cameron Simpson 

If God had intended Man to fly, He would have given him more money.
- Jeff Cauhape, cauh...@twg.com
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Re: how to download internet files by python ?

[Rodrick Brown]

On Mon, Jan 7, 2013 at 11:19 PM, iMath  wrote:

> for example ,if I want to download this file ,how to implement the
> download functionality by python ?
>
> http://down.51voa.com/201208/se-ed-foreign-students-friends-16aug12.mp3
>
> as for  download speed ,of course ,the fast ,the better ,so how to
> implement it ?
>
> It would be better to show me an example :) thanks !!!
> --
> http://mail.python.org/mailman/listinfo/python-list
>

#!/usr/bin/python
import urllib2
if __name__ == '__main__':
fileurl='
http://down.51voa.com/201208/se-ed-foreign-students-friends-16aug12.mp3'

mp3file = urllib2.urlopen(fileurl)
with open('outfile.mp3','wb') as output:
output.write(mp3file.read())
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Re: how to download internet files by python ?

[Roy Smith]

In article ,
 Cameron Simpson  wrote:

> On 07Jan2013 20:19, iMath  wrote:
> | for example ,if I want to download this file ,how to implement the download 
> | functionality by python ?
> | 
> | http://down.51voa.com/201208/se-ed-foreign-students-friends-16aug12.mp3
> | 
> | as for  download speed ,of course ,the fast ,the better ,so how to 
> | implement it ?
> | It would be better to show me an example :) thanks !!!
> 
> Look at urllib2.

Even better, look at requests 
(http://docs.python-requests.org/en/latest/).  There's nothing you can 
do with requests that you can't do with urllib2, but the interface is a 
whole lot easier to work with.
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comparison between non-comparable objects

[Kelvin Li]

The language reference says:

"...the choice whether one object [of built-in type] is considered
smaller or larger than another one is made arbitrarily..."

but that seems to be Python 2 behavior; Python 3 apparently raises a
TypeError. Does the documentation need updating?

Thanks,
Kelvin

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Re: comparison between non-comparable objects

[Dave Angel]

On 01/08/2013 12:28 AM, Kelvin Li wrote:
> The language reference says:
>
> "...the choice whether one object [of built-in type] is considered
> smaller or larger than another one is made arbitrarily..."

When quoting some online source, please give a reference link. It took
me a while to find the following page with your quote in it:


http://docs.python.org/3.3/reference/expressions.html

   in section "6.9  Comparisons"

> but that seems to be Python 2 behavior; Python 3 apparently raises a
> TypeError. Does the documentation need updating?
>

That sentence is correct in context.  The bullet items there are labeled
"Comparison of objects of the same type..."  And the particular bullet
also qualifies the type of the two objects being compared:   " Most
other objects of built-in types..."



Earlier in the same section, it considers the case of comparing objects
of DIFFERENT type.

 while the <, >, >= and <= operators raise a TypeError
 when
comparing objects of different types that do not implement these
operators for the given pair of types


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Re: [Offtopic] Line fitting [was Re: Numpy outlier removal]

[Chris Angelico]

On Tue, Jan 8, 2013 at 1:06 PM, Steven D'Aprano
 wrote:
>> given that weather patterns have been known to follow cycles at least
>> that long.
>
> That is not a given. "Weather patterns" don't last for thirty years.
> Perhaps you are talking about climate patterns?

Yes, that's what I meant. In any case, debate about global warming is
quite tangential to the point about statistical validity; it looks
quite significant to show a line going from the bottom of the graph to
the top, but sounds a lot less noteworthy when you see it as a
half-degree increase on about (I think?) 30 degrees, and even less
when you measure temperatures in absolute scale (Kelvin) and it's half
a degree in three hundred. Those are principles worth considering,
regardless of the subject matter. If your railway tracks have widened
by a full eight millimeters due to increased pounding from heavier
vehicles travelling over it, that's significant and dangerous on
HO-scale model trains, but utterly insignificant on 5'3" gauge.

ChrisA
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Re: comparison between non-comparable objects

[Kelvin Li]

> When quoting some online source, please give a reference link. It took
> me a while to find the following page with your quote in it:
> 
> 
> http://docs.python.org/3.3/reference/expressions.html
> 
>in section "6.9  Comparisons"

Sorry about that. Thanks for finding the link.

> > but that seems to be Python 2 behavior; Python 3 apparently raises a
> > TypeError. Does the documentation need updating?
> >
> 
> That sentence is correct in context.  The bullet items there are labeled
> "Comparison of objects of the same type..."  And the particular bullet
> also qualifies the type of the two objects being compared:   " Most
> other objects of built-in types..."

Got it, I was confusing built-in types with built-in functions--I
incorrectly thought object(), for example, returned an object of a
built-in type, and was behaving differently in Python 2 and 3:

object() < object()

Thanks,
Kelvin

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