Re: value of pi and 22/7

[peter]

On Mar 17, 5:22 pm, Kee Nethery  wrote:
> My favorite approximation is: 355/113  (visualize 113355 split into two 113 
> 355 and then do the division). The first 6 decimal places are the same.
>
> 3.141592920353982 = 355/113
> vs
> 3.1415926535897931
>
> Kee Nethery

Or (more for fun than any practical application) try (2143/22)^(1/4) =
3.14159265268.

Other approximations I have seen are root(10) and 3.142.  This last
was especially popular at school, which for me was sufficiently long
ago to have used four figure log tables.

The Old Testament (1 Kings 7,23) says ... "And he made a molten sea,
ten cubits from the one brim to the other: it was round all about, and
his height was five cubits: and a line of thirty cubits did compass it
round about. ".  So pi=3.  End Of.








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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[Duncan Booth]

Terry Reedy  wrote:

> On 3/17/2011 10:00 PM, Terry Reedy wrote:
>> On 3/17/2011 8:24 PM, J Peyret wrote:
>>> This gives a particularly nasty abend in Windows - "Python.exe has
>>> stopped working", rather than a regular exception stack error. I've
>>> fixed it, after I figured out the cause, which took a while, but 
maybe
>>> someone will benefit from this.
>>>
>>> Python 2.6.5 on Windows 7.
>>>
>>> class Foo(object):
>>> pass
>>>
>>> Foo.__repr__ = Foo.__str__ # this will cause an abend.
>>
>> 2.7.1 and 3.2.0 on winxp, no problem, interactive intepreter or IDLE
>> shell. Upgrade?
> 
> To be clear, the above, with added indent, but with extra fluff 
(fixes) 
> removed, is exactly what I ran. If you got error with anything else, 
> please say so. Described behavior for legal code is a bug. However, 
> unless a security issue, it would not be fixed for 2.6.
> 
On Windows, I can replicate this with Python 2.7, Python 3.1.2, and 
Python 3.2. Here's the exact script (I had to change the print to be 
compatible with Python 3.2):

 bug.py --
class Foo(object):
pass
#def __str__(self):  #if you have this defined, no abend
#return "a Foo"

Foo.__repr__ = Foo.__str__   # this will cause an abend.
#Foo.__str__ = Foo.__repr__  #do this instead, no abend

foo = Foo()
print(str(foo))

--

for Python 3.2 the command:
C:\Temp>c:\python32\python bug.py

generates a popup:

python.exe - Application Error
The exception unknown software exception (0xcfd) occurred in the 
application at location 0x1e08a325.

Click on OK to terminate the program
Click on CANCEL to debug the program

So it looks to me to be a current bug.

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Re: Fitting polynomial curve

[eryksun ()]

On 3/17/2011 1:42 AM, Astan Chee wrote:
>
> I have 2 points in 3D space and a bunch of points in-between them. I'm
> trying to fit a polynomial curve on it. Currently I'm looking through
> numpy but I don't think the function exists to fit a function like this:
> y = ax**4 + bx**3 + cx**2 + dx + e

You can use np.polyfit, which uses np.linalg.lstsq. 

For a degree M-1 polynomial and K samples such that K > M, this is an 
over-determined least squares problem:

t = [t1, t2, ..., tk]   # K sample times
Y.shape == (K, N)   # data samples Y in R_N

# design matrix X
# you don't have to calculate this since polyfit does it
# for you internally with vander(t, M)
X = [[x**m for m in range(M-1,-1,-1)] for x in t]
X.shape == (K, M)

# unknown coefficient matrix B
B.shape == (M, N)  

Y =~ dot(X, B) 

Use polyfit to form the least squares solution. For example, a 4th order fit:

B = np.polyfit(t, Y, 4)

# or for more information
B, r, rankX, sX, rcond = np.polyfit(t, Y, 4, full=True)

where r is the vector of residuals; rankX and sX are the rank and singular 
values of the Van der Monde matrix; and rcond was used to threshold the 
singular values.

Interpolation: 

t2 = np.linspace(t[0], t[-1], len(t)*1000)

Y2 = np.dot(np.vander(t2, M), B)
or 
Y2 = np.polyval(B, t2[:, newaxis])

polyval uses Horner's method, which calculates the following:

t = t2[:, newaxis]
y = zeros_like(t)

for i in range(len(B)):
y = y * t + B[i]
return y

y is initially a length len(t) column vector of zeros and B[0] is a length N 
row vector, so the first iteration just tiles B[0] in a len(t) by N matrix. 
Otherwise it's a normal Horner evaluation.

Other than minimizing the residuals, you can examine the fit visually with a 
simple matplotlib plot:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.gca(projection='3d')
ax.plot(*Y2.T)
ax.plot(*Y.T, marker='.', markerfacecolor='r')

Or you could create three 2D plots of (t2, Y2[:,i]) and (t, Y[:,i]).
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[eryksun ()]

On Thursday, March 17, 2011 8:24:36 PM UTC-4, J Peyret wrote:
>
> I suspect that object.__str__ is really object.__repr__ by default, as
> they both print out the same string, so that this doesn't make any
> sense.

They're not the same object, and they don't have all of the same methods. 

In [1]: object.__repr__ is object.__str__
Out[1]: False

In [2]: object.__repr__.__name__
Out[2]: '__repr__'

In [3]: object.__str__.__name__
Out[3]: '__str__'

In [4]: object.__repr__.__hash__()
Out[4]: 28910896

In [5]: object.__str__.__hash__()
Out[5]: 28910976

In [6]: object.__repr__.__call__(100)
Out[6]: ''

In [7]: object.__str__.__call__(100)
Out[7]: '100'
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Re: Multiprocessing.Process Daemonic Behavior

[Anssi Saari]

"John L. Stephens"  writes:

> As the parent process terminates 'normally' (either through normal
> termination or SIGINT termination), mulitprocessing steps in and
> performs child process cleanup via the x.terminate() method.  If the
> parent terminates any other way, multiprocessing doesn't have the
> opportunity to cleanup.

Unless you handle the signal explicitly? Since SIGINT maps to
KeyboardInterrupt automatically, you basically handle SIGINT but
nothing else. A rude hack to your example with a handler for SIGTERM
which just raises KeyboardInterrupt resulted in the children getting
the SIGTERM 10 seconds afterwards. Which is after the sleep(10) call
finishes in your script.

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Re: value of pi and 22/7

[Neil Cerutti]

On 2011-03-18, peter  wrote:
> The Old Testament (1 Kings 7,23) says ... "And he made a molten
> sea, ten cubits from the one brim to the other: it was round
> all about, and his height was five cubits: and a line of thirty
> cubits did compass it round about. ".  So pi=3.  End Of.

RIIght.  What's a cubit?

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Re: value of pi and 22/7

[Stefan Behnel]

Neil Cerutti, 18.03.2011 13:17:

On 2011-03-18, peter  wrote:

The Old Testament (1 Kings 7,23) says ... "And he made a molten
sea, ten cubits from the one brim to the other: it was round
all about, and his height was five cubits: and a line of thirty
cubits did compass it round about. ".  So pi=3.  End Of.


RIIght.  What's a cubit?


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

I think that particular author of that particular part of the bible just 
used it to make the text appear older than it was at the time.


Stefan

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Re: value of pi and 22/7

[Neil Cerutti]

On 2011-03-18, Stefan Behnel  wrote:
> Neil Cerutti, 18.03.2011 13:17:
>> On 2011-03-18, peter  wrote:
>>> The Old Testament (1 Kings 7,23) says ... "And he made a molten
>>> sea, ten cubits from the one brim to the other: it was round
>>> all about, and his height was five cubits: and a line of thirty
>>> cubits did compass it round about. ".  So pi=3.  End Of.
>>
>> RIIght.  What's a cubit?
>
> http://en.wikipedia.org/wiki/Cubit
>
> I think that particular author of that particular part of the
> bible just used it to make the text appear older than it was at
> the time.

http://www.youtube.com/watch?v=n0KHt8xrQkk

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Re: value of pi and 22/7

[Aage Andersen]

"peter"
Kee Nethery > My favorite approximation is: 355/113 (visualize 113355 split 
into two 113 355 and then do the division). The first 6 decimal places are 
the same.
>
> 3.141592920353982 = 355/113
> vs
> 3.1415926535897931
>
> Kee Nethery

Or (more for fun than any practical application) try (2143/22)^(1/4) =
3.14159265268.

Other approximations I have seen are root(10) and 3.142.  This last
was especially popular at school, which for me was sufficiently long
ago to have used four figure log tables.

The Old Testament (1 Kings 7,23) says ... "And he made a molten sea,
ten cubits from the one brim to the other: it was round all about, and
his height was five cubits: and a line of thirty cubits did compass it
round about. ".  So pi=3.  End Of.
---

3 is the best integer approximation to pi. So the bibel is right.

Aage












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Re: value of pi and 22/7

[Sherm Pendley]

Stefan Behnel  writes:

> Neil Cerutti, 18.03.2011 13:17:
>> On 2011-03-18, peter  wrote:
>>> The Old Testament (1 Kings 7,23) says ... "And he made a molten
>>> sea, ten cubits from the one brim to the other: it was round
>>> all about, and his height was five cubits: and a line of thirty
>>> cubits did compass it round about. ".  So pi=3.  End Of.
>>
>> RIIght.  What's a cubit?
>
> http://en.wikipedia.org/wiki/Cubit
>
> I think that particular author of that particular part of the bible
> just used it to make the text appear older than it was at the time.

Sigh. Doesn't *anyone* know Cosby any more? Kids today, no appreciation
for the classics. :-(

sherm--

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Re: value of pi and 22/7

[Westley Martínez]

On Fri, 2011-03-18 at 02:10 -0700, peter wrote:
> On Mar 17, 5:22 pm, Kee Nethery  wrote:
> > My favorite approximation is: 355/113  (visualize 113355 split into two 113 
> > 355 and then do the division). The first 6 decimal places are the same.
> >
> > 3.141592920353982 = 355/113
> > vs
> > 3.1415926535897931
> >
> > Kee Nethery
> 
> Or (more for fun than any practical application) try (2143/22)^(1/4) =
> 3.14159265268.
> 
> Other approximations I have seen are root(10) and 3.142.  This last
> was especially popular at school, which for me was sufficiently long
> ago to have used four figure log tables.
> 
> The Old Testament (1 Kings 7,23) says ... "And he made a molten sea,
> ten cubits from the one brim to the other: it was round all about, and
> his height was five cubits: and a line of thirty cubits did compass it
> round about. ".  So pi=3.  End Of.
> 
> 
> 
> 
> 
> 
> 
> 
The Bible uses integers due to memory constraints.

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Re: value of pi and 22/7

[Stefan Behnel]

Sherm Pendley, 18.03.2011 14:46:

Stefan Behnel writes:


Neil Cerutti, 18.03.2011 13:17:

On 2011-03-18, peter   wrote:

The Old Testament (1 Kings 7,23) says ... "And he made a molten
sea, ten cubits from the one brim to the other: it was round
all about, and his height was five cubits: and a line of thirty
cubits did compass it round about. ".  So pi=3.  End Of.


RIIght.  What's a cubit?


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

I think that particular author of that particular part of the bible
just used it to make the text appear older than it was at the time.


Sigh. Doesn't *anyone* know Cosby any more? Kids today, no appreciation
for the classics. :-(


And what about Heinz Erhardt? *That's* a classic.

Stefan

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Re: value of pi and 22/7

[Grant Edwards]

On 2011-03-18, peter  wrote:

> The Old Testament (1 Kings 7,23) says ... "And he made a molten sea,
> ten cubits from the one brim to the other: it was round all about, and
> his height was five cubits: and a line of thirty cubits did compass it
> round about. ".  So pi=3.  End Of.

There's nothing wrong with that value.  The measurements were given
with one significant digit, so the ratio of the two measurements
should only have one significant digit.

-- 
Grant Edwards   grant.b.edwardsYow! It's some people
  at   inside the wall!  This is
  gmail.combetter than mopping!
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Re: value of pi and 22/7

[Kee Nethery]

On Mar 18, 2011, at 5:17 AM, Neil Cerutti wrote:

> On 2011-03-18, peter  wrote:
>> The Old Testament (1 Kings 7,23) says ... "And he made a molten
>> sea, ten cubits from the one brim to the other: it was round
>> all about, and his height was five cubits: and a line of thirty
>> cubits did compass it round about. ".  So pi=3.  End Of.
> 
> RIIght.  What's a cubit?

I use cubits all the time. The distance from my elbow to my finger tips equals 
one cubit. When you don't have a proper measuring tape, it can be pretty 
accurate for comparing two measurements.

Kee Nethery


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Bounds checking

[Martin De Kauwe]

Hi,

if one has a set of values which should never step outside certain
bounds (for example if the values were negative then they wouldn't be
physically meaningful) is there a nice way to bounds check? I
potentially have 10 or so values I would like to check at the end of
each iteration. However as the loop is over many years I figured I
probably want to be as optimal as possible with my check. Any
thoughts?

e.g. this is my solution

# module contain data
# e.g. print state.something might produce 4.0
import state as state

def main():
for i in xrange(num_days):
# do stuff

# bounds check at end of iteration
bounds_check(state)


def bounds_check(state):
""" check state values are > 0 """
for attr in dir(state):
if not attr.startswith('__') and getattr(state, attr) < 0.0:
print "Error state values < 0: %s" % (attr)
sys.exit()

if __name__ == "__main__":
sys.exit(main())

thanks

Martin
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Re: value of pi and 22/7

[John Gordon]

In <8uh0rcfe1...@mid.individual.net> Neil Cerutti  writes:

> RIIght.  What's a cubit?

How long can you tread water?

-- 
John Gordon   A is for Amy, who fell down the stairs
gor...@panix.com  B is for Basil, assaulted by bears
-- Edward Gorey, "The Gashlycrumb Tinies"

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Re: Bounds checking

[Katie T]

What sort of checks are you making ?  - in general greater than/less than
tend to be fairly optimal, although you might be able to do a faster "is
negative" test

Katie

On Fri, Mar 18, 2011 at 2:24 PM, Martin De Kauwe  wrote:

> Hi,
>
> if one has a set of values which should never step outside certain
> bounds (for example if the values were negative then they wouldn't be
> physically meaningful) is there a nice way to bounds check? I
> potentially have 10 or so values I would like to check at the end of
> each iteration. However as the loop is over many years I figured I
> probably want to be as optimal as possible with my check. Any
> thoughts?
>
> e.g. this is my solution
>
> # module contain data
> # e.g. print state.something might produce 4.0
> import state as state
>
> def main():
>for i in xrange(num_days):
># do stuff
>
># bounds check at end of iteration
>bounds_check(state)
>
>
> def bounds_check(state):
>""" check state values are > 0 """
>for attr in dir(state):
>if not attr.startswith('__') and getattr(state, attr) < 0.0:
>print "Error state values < 0: %s" % (attr)
>sys.exit()
>
> if __name__ == "__main__":
>sys.exit(main())
>
> thanks
>
> Martin
> --
> http://mail.python.org/mailman/listinfo/python-list
>



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Re: Bounds checking

[Jean-Michel Pichavant]

Martin De Kauwe wrote:

Hi,

if one has a set of values which should never step outside certain
bounds (for example if the values were negative then they wouldn't be
physically meaningful) is there a nice way to bounds check? I
potentially have 10 or so values I would like to check at the end of
each iteration. However as the loop is over many years I figured I
probably want to be as optimal as possible with my check. Any
thoughts?

e.g. this is my solution

# module contain data
# e.g. print state.something might produce 4.0
import state as state

def main():
for i in xrange(num_days):
# do stuff

# bounds check at end of iteration
bounds_check(state)


def bounds_check(state):
""" check state values are > 0 """
for attr in dir(state):
if not attr.startswith('__') and getattr(state, attr) < 0.0:
print "Error state values < 0: %s" % (attr)
sys.exit()

if __name__ == "__main__":
sys.exit(main())

thanks

Martin
  
Don't check for bounds, fix any bug in the code that would set your 
values out of bounds and use asserts while debugging.


Otherwise if you really need dynamic checks, it will cost you cpu, for 
sure. Howeverver you could for instance override the __setatttr__ of 
state object, and call the attribute's associated function.


class State(object):
   funcTable = {
  'foo': lambda x: x >= 0.0
   }
  
   def __init__(self):

  self.foo = 0

   def __setattr__(self, attribute, value):
  if not self.funcTable.get(attribute, lambda x: True)(value):
  sys.exit('error out of bound')
  return object.__setattr(self, attribute, value)


Untested, however it's just an idea. I'm not even sure that would be 
less cpu consuming :D
That way only attributes in functable execute a (cpu consuming ?) test 
function, all other attributes will execute 'lambda x: True'.


The check occurs everytime you set an attribute however.

JM
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Re: Bounds checking

[Mel]

Jean-Michel Pichavant wrote:
> Martin De Kauwe wrote:

> Don't check for bounds, fix any bug in the code that would set your
> values out of bounds and use asserts while debugging.
[ ... ]
> def __setattr__(self, attribute, value):
>if not self.funcTable.get(attribute, lambda x: True)(value):
>sys.exit('error out of bound')
>return object.__setattr(self, attribute, value)

Offhand, my only quibble is that sys.exit is not helpful for debugging.  
Much better to raise an error:

if not self.funcTable.get(attribute, lambda x: True)(value):
raise ValueError ('error out of bound')

or define a subclass of ValueError just for this purpose.  On error, the 
program will stop just as dead, but you'll get a trace.

Mel.
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Re: value of pi and 22/7

[Adam Tauno Williams]

On Fri, 2011-03-18 at 14:16 +, Grant Edwards wrote:
> On 2011-03-18, peter  wrote:
> > The Old Testament (1 Kings 7,23) says ... "And he made a molten sea,
> > ten cubits from the one brim to the other: it was round all about, and
> > his height was five cubits: and a line of thirty cubits did compass it
> > round about. ".  So pi=3.  End Of.
> There's nothing wrong with that value.  The measurements were given
> with one significant digit, so the ratio of the two measurements
> should only have one significant digit.

I've worked in landscaping and [low-scale] agriculture - pi as 3 is used
all the time.  It is easy to compute in your head and close enough.  


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Re: email library

[Ethan Furman]

peterob wrote:

Im completely confinvalided from email library. When you parse email from
file it creates object Message.

f = open(emailFile, 'r')
msg = email.message_from_file(f)
f.close()


How can I access RAW header of email represented by object msg? I dont
wanna access each header field by hand.

Im doing another parsing, searching for attachments and so on, with
email, but i need write raw data of email too. Do I have to allocate
another memory for that emailFile? (by mmap or f=open(rawemail).


For the ultimate in raw, open the email file and parse it manually.

Your other option is use msg.walk() and msg.items() and walk through the 
returned (header, value) pairs.


8<-
--> import email
--> msg = email.message_from_file(open(r'c:\temp2\latest_dbf.eml'))
--> from pprint import pprint as pp
--> for sub in msg.walk():
...   pp(sub.items())
...
[('Return-path', ''),
 ('Envelope-to', 'someone@somewhere.invalid'),
 ('Delivery-date', 'Mon, 07 Mar 2011 18:32:18 -0600'),
 ('Received',
  'from [72.11.125.166] (port=2728 helo=[192.168.10.136])\n\tby 
gator410.hostgator.com with esmtpa (Exim 4.69)\n\t(envelope-from 
)\n\tid
 1PwkqN-0001eV-54\n\tfor someone@somewhere.invalid; Mon, 07 Mar 2011 
18:32:16 -0600'),

 ('Message-ID', '<4D757B80.9020001@somewhere.invalid>'),
 ('Date', 'Mon, 07 Mar 2011 16:42:40 -0800'),
 ('From', 'First Last '),
 ('User-Agent', 'Thunderbird 1.5.0.10 (Windows/20070221)'),
 ('MIME-Version', '1.0'),
 ('To', 'First Last '),
 ('Subject', 'latest dbf'),
 ('Content-Type',
  'multipart/mixed;\n boundary="010408020108000602070901"')]

[('Content-Type', 'text/plain; charset=ISO-8859-1; format=flowed'),
 ('Content-Transfer-Encoding', '7bit')]

[('Content-Type', 'text/plain;\n name="tables.py"'),
 ('Content-Transfer-Encoding', '7bit'),
 ('Content-Disposition', 'inline;\n filename="tables.py"')]

[('Content-Type', 'application/x-zip-compressed;\n name="dbf-0.88.18.zip"'),
 ('Content-Transfer-Encoding', 'base64'),
 ('Content-Disposition', 'inline;\n filename="dbf-0.88.18.zip"')]
8<-

Hope this helps!

~Ethan~
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Remove all directories using wildcard

[JSkinn3]

I'm new to python and I am trying to figure out how to remove all sub
directories from a parent directory using a wildcard.  For example,
remove all sub directory folders that contain the word "PEMA" from the
parent directory "C:\Data".

I've trying to use os.walk with glob, but I'm not sure if this is the
right path to take.

Thanks for any suggestions!
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Re: Remove all directories using wildcard

[Tim Golden]

On 18/03/2011 16:41, JSkinn3 wrote:

I'm new to python and I am trying to figure out how to remove all sub
directories from a parent directory using a wildcard.  For example,
remove all sub directory folders that contain the word "PEMA" from the
parent directory "C:\Data".

I've trying to use os.walk with glob, but I'm not sure if this is the
right path to take.


You've got a few options. And it depends whether you just want
to get it done as simply as possible or whether you're using
this as a learning exercise.

Assuming it's somewhere between the two then you're on the right
track with os.walk:


import os
import shutil

for dirpath, dirnames, filenames in os.walk ("c:/data"):
  for dirname in dirnames:
if "pema" in dirname.lower ():
  pema_path = os.path.join (dirpath, dirname)
  print "Removing", pema_path
  shutil.rmtree (pema_path)
  dirnames.remove (dirname)



The key is that os.walk is designed so that the dirnames
list can be mutated in place to remove directories which
are to be ignored for whatever reason. In this case, you
delete the directory tree and remove it from os.walk's
attention.

BTW the use of os.walk here is only necessary if you need to
remove "*pema*" directories at any level under c:\data. If
you only need those immediately under c:\data then you can
just use glob.glob in union with shutil.rmtree

TJG
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RE: Remove all directories using wildcard

[Andreas Tawn]

> I'm new to python and I am trying to figure out how to remove all sub
> directories from a parent directory using a wildcard.  For example,
> remove all sub directory folders that contain the word "PEMA" from the
> parent directory "C:\Data".
> 
> I've trying to use os.walk with glob, but I'm not sure if this is the
> right path to take.
> 
> Thanks for any suggestions!

I think I'd do something like this (untested).

import os, shutil

startDir = r"C:\Data"

for item in os.listdir(startDir):
folder = os.path.join(startDir, item)
if os.path.isdir(folder) and "PEMA" in item:
shutil.rmtree(folder)

Cheers,

Drea
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multiprocessing Pool workers cannot create subprocesses

[Jason Grout]

In a recent application, a student of mine tried to create child 
processes inside of a multiprocessing Pool worker (for security and 
convenience reasons, we wanted to run some code inside of a child 
process).  Here is some test code for python 2.7:


=
import multiprocessing as mp

def run_computation(x):
print 2*x

def f(x):
curr_proc=mp.current_process()
# uncomment following line to get this to work
#curr_proc.daemon=False

p = mp.Process(target=run_computation, args=(x,))
p.start()
p.join()


pool = mp.Pool(processes=4)
pool.map(f, range(10))

===

The result is:

Traceback (most recent call last):
  File "daemon.py", line 17, in 
pool.map(f, range(10))
  File 
"/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/multiprocessing/pool.py", 
line 199, in map

return self.map_async(func, iterable, chunksize).get()
  File 
"/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/multiprocessing/pool.py", 
line 491, in get

raise self._value
AssertionError: daemonic processes are not allowed to have children

The problem appears to be that multiprocessing sets its workers to have 
the daemon flag set to True, which prevents workers from creating child 
processes.  If I uncomment the line indicated in the code, I can create 
child processes and the program works (it prints out the even numbers 
from 0 to 18).


It makes me nervous to just change the daemon status of the process like 
that, especially when I don't know the reason the workers have 
daemon=True to begin with.  What is the reasoning behind that decision? 
 What issues do we need to worry about if we just set the daemon mode 
flag like in the above code?


Thanks,

Jason
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Re: Bounds checking

[Miki Tebeka]

> def bounds_check(state):
> """ check state values are > 0 """
> for attr in dir(state):
> if not attr.startswith('__') and getattr(state, attr) < 0.0:
> print "Error state values < 0: %s" % (attr)
> sys.exit()
Not that related to the question. But it's usually better to raise an exception.
Exiting in the middle of a function usually make debugging later more 
"interesting".

You might find Traits interesting for validation, see 
http://code.enthought.com/projects/traits/

HTH
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ctypes pointer to structure memory swap

[Wanderer]

I'm observing some strange behavior with ctypes. I created this test
code to try to figure out what I'm doing wrong creating pointers to
structures.

from ctypes import *

class QCamSettingId(Structure):
""" QCam_settings_id
"""
_fields_ = [("f1", c_ulong),
("f2", c_ushort),
("f3", c_ushort),
("f4", c_ubyte * 8)]


class QCamSettingsEx(Structure):
""" QCam_SettingsEx
"""
_fields_ = [("size", c_ulong), # Filled by
the init routine
("pSettingsID", POINTER(QCamSettingId)),   # pointer
to the camera settings ID
("private_data", c_void_p )]   # Pointer
to a camera settings array

class QMemDriver():
""" The wrapper of QCamDriver
"""
def __init__(self):

self.QSetID = QCamSettingId()
self.QSetID_p = pointer(self.QSetID)
self.QSettings = QCamSettingsEx()
self.QSettings.pSettingsID = self.QSetID_p
self.QSettings_p = pointer(self.QSettings)

def Test(self):
"""
Test the QCamSettinsEx object
"""
print self.QSettings.pSettingsID
print self.QSettings.pSettingsID[0]
print self.QSettings.pSettingsID
print self.QSettings.pSettingsID[0]
print "pSettingsID is at", self.QSettings.pSettingsID
print "pSettingsID[0] is at", self.QSettings.pSettingsID[0]
print "pSettingsID is at", self.QSettings.pSettingsID
print "pSettingsID[0] is at", self.QSettings.pSettingsID[0]


The results I get are.

>>> qmem.Test()




pSettingsID is at 
pSettingsID[0] is at 
pSettingsID is at 
pSettingsID[0] is at 
>>> qmem = QMEMTest.QMemDriver()
>>> qmem.Test()




pSettingsID is at 
pSettingsID[0] is at 
pSettingsID is at 
pSettingsID[0] is at 

Sometimes the pointer and the object swap location and sometimes they
don't.
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Re: Bounds checking

[Katie T]

On Fri, Mar 18, 2011 at 3:01 PM, Jean-Michel Pichavant <
jeanmic...@sequans.com> wrote:
>
> Don't check for bounds, fix any bug in the code that would set your values
> out of bounds and use asserts while debugging.
>
> Otherwise if you really need dynamic checks, it will cost you cpu, for
> sure. Howeverver you could for instance override the __setatttr__ of state
> object, and call the attribute's associated function.
>

If the codes something critical (i.e. it's used for financial calculations,
hardware control, etc.) it's probably safer to test it dynamically, unless
you only have a finite number of inputs/outputs it's often hard to ensure
you've fixed all the bugs.

Katie
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Re: Two random lists from one list

[noydb]

Thanks All for your responses, all a help!
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Could I joined in this Happy family

[duxiu xiang]

Dear friends:
  I am in China.For some rearon,I cannot visit your Google Group.May
I joint this mail list for help in learning Python?

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Re: Could I joined in this Happy family

[Nick Stinemates]

Welcome aboard !
On Mar 18, 2011 11:34 AM, "duxiu xiang"  wrote:
> Dear friends:
> I am in China.For some rearon,I cannot visit your Google Group.May
> I joint this mail list for help in learning Python?
>
> --
> 笑看嫣红染半山，逐风万里白云间。
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class error

[monkeys paw]

I have the following file:

FileInfo.py:

import UserDict

class FileInfo(UserDict):
"store file metadata"
def __init__(self, filename=None):
UserDict.__init__(self)
self["name"] = filename



When i import it like so:

import FileInfo


i get this error:

Traceback (most recent call last):
  File "", line 1, in 
  File "FileInfo.py", line 3, in 
class FileInfo(UserDict):
TypeError: Error when calling the metaclass bases
module.__init__() takes at most 2 arguments (3 given)

What is causing the error?
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Re: multiprocessing Pool workers cannot create subprocesses

[Ned Deily]

In article <4d838d28.5090...@creativetrax.com>,
 Jason Grout  wrote:
> The problem appears to be that multiprocessing sets its workers to have 
> the daemon flag set to True, which prevents workers from creating child 
> processes.  If I uncomment the line indicated in the code, I can create 
> child processes and the program works (it prints out the even numbers 
> from 0 to 18).
> 
> It makes me nervous to just change the daemon status of the process like 
> that, especially when I don't know the reason the workers have 
> daemon=True to begin with.  What is the reasoning behind that decision? 
>   What issues do we need to worry about if we just set the daemon mode 
> flag like in the above code?

http://docs.python.org/library/multiprocessing.html#multiprocessing.Proce
ss.daemon

"When a process exits, it attempts to terminate all of its daemonic 
child processes.

Note that a daemonic process is not allowed to create child processes. 
Otherwise a daemonic process would leave its children orphaned if it 
gets terminated when its parent process exits. Additionally, these are 
not Unix daemons or services, they are normal processes that will be 
terminated (and not joined) if non-daemonic processes have exited."

-- 
 Ned Deily,
 n...@acm.org

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Re: class error

[MRAB]

On 18/03/2011 20:13, monkeys paw wrote:

I have the following file:

FileInfo.py:

import UserDict

class FileInfo(UserDict):
"store file metadata"
def __init__(self, filename=None):
UserDict.__init__(self)
self["name"] = filename



When i import it like so:

import FileInfo


i get this error:

Traceback (most recent call last):
  File "", line 1, in 
  File "FileInfo.py", line 3, in 
class FileInfo(UserDict):
TypeError: Error when calling the metaclass bases
module.__init__() takes at most 2 arguments (3 given)

What is causing the error?


You're importing the module "UserDict" and then trying to create a
subclass of it.

The module "UserDict" contains the class "UserDict".

You could write either:

import UserDict

class FileInfo(UserDict.UserDict):

or:

from UserDict import UserDict

class FileInfo(UserDict):
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Re: class error

[Ethan Furman]

monkeys paw wrote:

I have the following file:

FileInfo.py:

import UserDict

class FileInfo(UserDict):
"store file metadata"
def __init__(self, filename=None):
UserDict.__init__(self)
self["name"] = filename



When i import it like so:

import FileInfo


i get this error:

Traceback (most recent call last):
  File "", line 1, in 
  File "FileInfo.py", line 3, in 
class FileInfo(UserDict):
TypeError: Error when calling the metaclass bases
module.__init__() takes at most 2 arguments (3 given)

What is causing the error?


UserDict is a module -- you want to subclass the UserDict class inside 
the module...


class FileInfo(UserDict.UserDict):
"etc etc"

~Ethan~
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Re: class error

[Alexander Kapps]

On 18.03.2011 21:13, monkeys paw wrote:

I have the following file:

FileInfo.py:

import UserDict


After this import statement, the name "UserDict" refers to the module.


class FileInfo(UserDict):


Here you are trying to subclass the module. What you need instead is:

class FileInfo(UserDict.UserDict):

Alternatively, import the UserDict class from the UserDict module 
like so:


from UserDict import UserDict

Note, that the UserDict class is obsolete, you can subclass the dict 
type directly:


class FileInfo(dict):
"store file metadata"
def __init__(self, filename=None):
dict.__init__(self)
self["name"] = filename
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[Carl Banks]

On Mar 18, 2:18 am, Duncan Booth  wrote:
> Terry Reedy  wrote:
> > On 3/17/2011 10:00 PM, Terry Reedy wrote:
> >> On 3/17/2011 8:24 PM, J Peyret wrote:
> >>> This gives a particularly nasty abend in Windows - "Python.exe has
> >>> stopped working", rather than a regular exception stack error. I've
> >>> fixed it, after I figured out the cause, which took a while, but
> maybe
> >>> someone will benefit from this.
>
> >>> Python 2.6.5 on Windows 7.
>
> >>> class Foo(object):
> >>> pass
>
> >>> Foo.__repr__ = Foo.__str__ # this will cause an abend.
>
> >> 2.7.1 and 3.2.0 on winxp, no problem, interactive intepreter or IDLE
> >> shell. Upgrade?
>
> > To be clear, the above, with added indent, but with extra fluff
> (fixes)
> > removed, is exactly what I ran. If you got error with anything else,
> > please say so. Described behavior for legal code is a bug. However,
> > unless a security issue, it would not be fixed for 2.6.
>
> On Windows, I can replicate this with Python 2.7, Python 3.1.2, and
> Python 3.2. Here's the exact script (I had to change the print to be
> compatible with Python 3.2):
>
>  bug.py --
> class Foo(object):
>     pass
>     #def __str__(self):  #if you have this defined, no abend
>     #    return "a Foo"
>
> Foo.__repr__ = Foo.__str__   # this will cause an abend.
> #Foo.__str__ = Foo.__repr__  #do this instead, no abend
>
> foo = Foo()
> print(str(foo))
>
> --
>
> for Python 3.2 the command:
>     C:\Temp>c:\python32\python bug.py
>
> generates a popup:
>
>     python.exe - Application Error
>     The exception unknown software exception (0xcfd) occurred in the
>     application at location 0x1e08a325.
>
>     Click on OK to terminate the program
>     Click on CANCEL to debug the program
>
> So it looks to me to be a current bug.

Multiple people reproduce a Python hang/crash yet it looks like no one
bothered to submit a bug report

I observed the same behavior (2.6 and 3.2 on Linux, hangs) and went
ahead and submitted a bug report.


Carl Banks
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Re: class error

[monkeys paw]

On 3/18/2011 4:43 PM, Alexander Kapps wrote:

On 18.03.2011 21:13, monkeys paw wrote:

I have the following file:

FileInfo.py:

import UserDict


After this import statement, the name "UserDict" refers to the module.


class FileInfo(UserDict):


Here you are trying to subclass the module. What you need instead is:

class FileInfo(UserDict.UserDict):


OK, i overlooked that and the error was not very enlightening.
Thanks very much.



Alternatively, import the UserDict class from the UserDict module like so:

from UserDict import UserDict

Note, that the UserDict class is obsolete, you can subclass the dict
type directly:

class FileInfo(dict):
"store file metadata"
def __init__(self, filename=None):
dict.__init__(self)
self["name"] = filename


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Reading/Writing files

[Jon Herman]

Hello all,

I am pretty new to Python and am trying to write data to a file. However, I
seem to be misunderstanding how to do so. For starters, I'm not even sure
where Python is looking for these files or storing them. The directories I
have added to my PYTHONPATH variable (where I import modules from
succesfully) does not appear to be it.

So my question is: How do I tell Python where to look for opening files, and
where to store new files?

Thanks,

Jon
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Re: ctypes pointer to structure memory swap

[Nobody]

On Fri, 18 Mar 2011 10:34:35 -0700, Wanderer wrote:

> I'm observing some strange behavior with ctypes. I created this test
> code to try to figure out what I'm doing wrong creating pointers to
> structures.

What makes you think that you're doing anything wrong.

Note that the hex number shown when printing a ctypes object is the
object's ID (as per the id() function). This is typically the address of
the Python object. It is not the address of the structured data nor (in
the case of a ctypes pointer) the value of the pointer.

If you want to see the actual value of a ctypes pointer, cast it to
c_void_p then examine the .value field, e.g.:

p = pointer(x)
print hex(cast(p, c_void_p).value)


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Use cookies from a script in a browser

[gervaz]

Hi all,
I use a scraper to retrieve data from a web page.
In order to do that I need to enable cookies.
The data that I'm looking for is contained in a bunch of web pages.
Is there a way to show this web pages in a browser using the cookies
used in the script (otherwise it doesn't work).

Thanks,

Mattia
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Re: Reading/Writing files

[Matt Chaput]

On 18/03/2011 5:33 PM, Jon Herman wrote:

I am pretty new to Python and am trying to write data to a file.
However, I seem to be misunderstanding how to do so. For starters, I'm
not even sure where Python is looking for these files or storing them.
The directories I have added to my PYTHONPATH variable (where I import
modules from succesfully) does not appear to be it.

So my question is: How do I tell Python where to look for opening files,
and where to store new files?


This is how you write to a file in Python

myfile = open("path/to/the/file", "wb")
myfile.write("Hello world!\n")
myfile.close()

Beyond that, your message is too vague to offer any real help, but it 
sounds like you're way off track. If the above code doesn't help, please 
tell us exactly what you're trying to do, but you might want to read a 
Python book such as Dive Into Python first.


Cheers,

Matt


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Re: Reading/Writing files

[Jack Trades]

On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman  wrote:

> Hello all,
>
> I am pretty new to Python and am trying to write data to a file. However, I
> seem to be misunderstanding how to do so. For starters, I'm not even sure
> where Python is looking for these files or storing them. The directories I
> have added to my PYTHONPATH variable (where I import modules from
> succesfully) does not appear to be it.
>
> So my question is: How do I tell Python where to look for opening files,
> and where to store new files?
>
> Thanks,
>
> Jon
>
>
By default Python will read and write files from the directory that your
program is run from.  This cannot always be relied upon though (for instance
if your program was imported as a module from another program).

To find out what directory your program is currently in use os.getcwd().
Here's an example I just ran...

>>> import os
>>> os.getcwd()
'/media/DATA/code/lispy/liSpy'

The folder that is returned from os.getcwd() is the folder that "open" will
use.  You can specify another folder by giving the full path.

open("/full/path/to/file.txt", "w")

PYTHONPATH is for importing modules, which is a separate concern.

-- 
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Pointless Programming Blog 
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Re: Reading/Writing files

[Ethan Furman]

Jon Herman wrote:

Hello all,

I am pretty new to Python and am trying to write data to a file. 
However, I seem to be misunderstanding how to do so. For starters, I'm 
not even sure where Python is looking for these files or storing them. 
The directories I have added to my PYTHONPATH variable (where I import 
modules from succesfully) does not appear to be it.


So my question is: How do I tell Python where to look for opening files, 
and where to store new files?


There's nothing magical about it (plenty of irritating and frustrating 
if using Windows, though ;).


somefile = open('test.txt') # opens file test.txt in current directory
someotherfile = open('./stuff/misc.txt') # opens misc.txt, which lives
 # in stuff which lives in the
 # the current directory
thatfile = open(r'c:\blah\whodunit.clu') # opens whodunit.clu which
 # lives in blah off the C:
 # drive

To get the current directory, if you don't know what it is:

import os
os.getcwd()

and if you want to change the current directory:

os.chdir('/some/new/path')

~Ethan~
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Re: Use cookies from a script in a browser

[Miki Tebeka]

You can use mechanize, which holds a cookie jar and can user the browser 
cookies as well.
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Re: Reading/Writing files

[Jon Herman]

Jack,

thanks.

Alright, so what I did is create a file called hello.txt with a single line
of text in there. I then did the following:

f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
full directory on my computer)
open("f", "w")

And I get the following error: IOError: [Errno 13] Permission denied: 'f'
If I open to read, I get: IOError: [Errno 2] No such file or directory: 'f'

Can anyone explain to me why this happens?




On Fri, Mar 18, 2011 at 3:50 PM, Jack Trades wrote:

>
> On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman  wrote:
>
>> Hello all,
>>
>> I am pretty new to Python and am trying to write data to a file. However,
>> I seem to be misunderstanding how to do so. For starters, I'm not even sure
>> where Python is looking for these files or storing them. The directories I
>> have added to my PYTHONPATH variable (where I import modules from
>> succesfully) does not appear to be it.
>>
>> So my question is: How do I tell Python where to look for opening files,
>> and where to store new files?
>>
>> Thanks,
>>
>> Jon
>>
>>
> By default Python will read and write files from the directory that your
> program is run from.  This cannot always be relied upon though (for instance
> if your program was imported as a module from another program).
>
> To find out what directory your program is currently in use os.getcwd().
> Here's an example I just ran...
>
> >>> import os
> >>> os.getcwd()
> '/media/DATA/code/lispy/liSpy'
>
> The folder that is returned from os.getcwd() is the folder that "open" will
> use.  You can specify another folder by giving the full path.
>
> open("/full/path/to/file.txt", "w")
>
> PYTHONPATH is for importing modules, which is a separate concern.
>
> --
> Jack Trades
> Pointless Programming Blog 
>
>
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Re: Reading/Writing files

[Jack Trades]

On Fri, Mar 18, 2011 at 4:56 PM, Jon Herman  wrote:

> Jack,
>
> thanks.
>
> Alright, so what I did is create a file called hello.txt with a single line
> of text in there. I then did the following:
>
> f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
> full directory on my computer)
> open("f", "w")
>
> And I get the following error: IOError: [Errno 13] Permission denied: 'f'
> If I open to read, I get: IOError: [Errno 2] No such file or directory: 'f'
>
> Can anyone explain to me why this happens?
>
>
You need to remove the quotes from f.  f is a variable name, not a string,
so there should be no quotes around it.

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Re: Reading/Writing files

[Dan Stromberg]

For open() or os.open(), it should look in your Current Working Directory
(CWD).  Your python's CWD defaults to what the CWD was when python was
started, and it is changed with os.chdir().

Absolute paths will of course be relative to / on most OS's (or C:/ if
you're on C:, D:/ if you're on D:, etc. - IOW Windows is more complicated),
and relative paths will be relative to your CWD.

On Fri, Mar 18, 2011 at 2:33 PM, Jon Herman  wrote:

> Hello all,
>
> I am pretty new to Python and am trying to write data to a file. However, I
> seem to be misunderstanding how to do so. For starters, I'm not even sure
> where Python is looking for these files or storing them. The directories I
> have added to my PYTHONPATH variable (where I import modules from
> succesfully) does not appear to be it.
>
> So my question is: How do I tell Python where to look for opening files,
> and where to store new files?
>
> Thanks,
>
> Jon
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
>
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Re: Reading/Writing files

[Jack Trades]

On Fri, Mar 18, 2011 at 4:59 PM, Jack Trades wrote:

>
>
> On Fri, Mar 18, 2011 at 4:56 PM, Jon Herman  wrote:
>
>> Jack,
>>
>> thanks.
>>
>> Alright, so what I did is create a file called hello.txt with a single
>> line of text in there. I then did the following:
>>
>> f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
>> full directory on my computer)
>> open("f", "w")
>>
>> And I get the following error: IOError: [Errno 13] Permission denied: 'f'
>> If I open to read, I get: IOError: [Errno 2] No such file or directory:
>> 'f'
>>
>> Can anyone explain to me why this happens?
>>
>>
> You need to remove the quotes from f.  f is a variable name, not a string,
> so there should be no quotes around it.
>
>
> --
> Jack Trades
> Pointless Programming Blog 
>
>
Sorry I should have given an example.  From your code it should look like
this...

filename = "fulldirectory\hello.txt"

You then use f to write or read.  This is how you read...

f = open(filename, "r")
file_contents = f.read()
f.close()

and this is how you write...

f = open(filename, "w")
f.write("hello world")
f.close()

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Re: Reading/Writing files

[Dan Stromberg]

Are you on windows?

You probably should use / as your directory separator in Python, not \.  In
Python, and most other programming languages, \ starts an escape sequence,
so to introduce a literal \, you either need to prefix your string with r
(r"\foo\bar") or double your backslashes ("\\foo\\bar").

/ works fine on windows, and doesn't require escaping ("/foo/bar").

On Fri, Mar 18, 2011 at 2:56 PM, Jon Herman  wrote:

> Jack,
>
> thanks.
>
> Alright, so what I did is create a file called hello.txt with a single line
> of text in there. I then did the following:
>
> f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
> full directory on my computer)
> open("f", "w")
>
> And I get the following error: IOError: [Errno 13] Permission denied: 'f'
> If I open to read, I get: IOError: [Errno 2] No such file or directory: 'f'
>
> Can anyone explain to me why this happens?
>
>
>
>
>
> On Fri, Mar 18, 2011 at 3:50 PM, Jack Trades 
> wrote:
>
>>
>> On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman  wrote:
>>
>>> Hello all,
>>>
>>> I am pretty new to Python and am trying to write data to a file. However,
>>> I seem to be misunderstanding how to do so. For starters, I'm not even sure
>>> where Python is looking for these files or storing them. The directories I
>>> have added to my PYTHONPATH variable (where I import modules from
>>> succesfully) does not appear to be it.
>>>
>>> So my question is: How do I tell Python where to look for opening files,
>>> and where to store new files?
>>>
>>> Thanks,
>>>
>>> Jon
>>>
>>>
>> By default Python will read and write files from the directory that your
>> program is run from.  This cannot always be relied upon though (for instance
>> if your program was imported as a module from another program).
>>
>> To find out what directory your program is currently in use os.getcwd().
>> Here's an example I just ran...
>>
>> >>> import os
>> >>> os.getcwd()
>> '/media/DATA/code/lispy/liSpy'
>>
>> The folder that is returned from os.getcwd() is the folder that "open"
>> will use.  You can specify another folder by giving the full path.
>>
>> open("/full/path/to/file.txt", "w")
>>
>> PYTHONPATH is for importing modules, which is a separate concern.
>>
>> --
>> Jack Trades
>> Pointless Programming Blog 
>>
>>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
>
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Re: ctypes pointer to structure memory swap

[Wanderer]

On Mar 18, 5:48 pm, Nobody  wrote:
> On Fri, 18 Mar 2011 10:34:35 -0700, Wanderer wrote:
> > I'm observing some strange behavior with ctypes. I created this test
> > code to try to figure out what I'm doing wrong creating pointers to
> > structures.
>
> What makes you think that you're doing anything wrong.
>
> Note that the hex number shown when printing a ctypes object is the
> object's ID (as per the id() function). This is typically the address of
> the Python object. It is not the address of the structured data nor (in
> the case of a ctypes pointer) the value of the pointer.
>
> If you want to see the actual value of a ctypes pointer, cast it to
> c_void_p then examine the .value field, e.g.:
>
>         p = pointer(x)
>         print hex(cast(p, c_void_p).value)

In the real program the pointer to the structure is passed to the DLL.
The DLL has functions CreateCameraSettingsStruct and
ReleaseCameraSettingsStruct. Once I call CreateCameraSettingStruct, I
can't delete the pointer without crashing Python. Calling
ReleaseCameraSettingStruct doesn't help. The result is the program
crashes on exit during the class destruction. I was trying to figure
out why ReleaseCameraSettingStruct doesn't release the pointer so
Python can close the program. I was checking to see what happened
before and after ReleaseCameraSettingStruct and saw this. But it
happens even if I don't run ReleaseCameraSettingStruct.

Thanks for the reply, but I'm still not sure I understand. Why should
Object1 be at address1 and Object2 be at address2 and the next moment
Object2 is at address1 and Object1 is at address2? I'll try casting
them to see what the value is before and after calling
ReleaseCameraSettingStruct.

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Re: Reading/Writing files

[Alexander Kapps]

On 18.03.2011 22:33, Jon Herman wrote:

Hello all,

I am pretty new to Python and am trying to write data to a file. However, I
seem to be misunderstanding how to do so. For starters, I'm not even sure
where Python is looking for these files or storing them. The directories I
have added to my PYTHONPATH variable (where I import modules from
succesfully) does not appear to be it.

So my question is: How do I tell Python where to look for opening files, and
where to store new files?

Thanks,

Jon





There is no special place where Python looks for normal files 
(PYTHONPATH is just tells where to look for modules.)


If you open a file (for reading and/or writing) and don't give an 
absolute path, then the filename is relative to the CWD (Current 
Working Directory). One can change this directory with os.chdir() 
*but* you shouldn't need to do that. Either start Python in the 
desired directory (your operating system will have a way to do this 
for icons and menu entries) or give an absolute path like:


f = open("/home/alex/test.txt")
f = open("c:/test.txt")

Also check out os.environ, a dict containing the environment 
variables. There you will find variables like $HOME or %USERPROFILE% 
(if that's correct) which tells where your personal files are:


import os

# my home directory is /home/alex
homedir = os.environ["HOME"]

# creates the file /home/alex/test.txt
f = open(os.path.join(homedir, "test.txt"))
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Re: Reading/Writing files

[Jon Herman]

Folks,

thanks for the many responses! Specifying the full file name (and not using
parentheses when inappropriate, thanks Jack :)) I am now happily
reading/writing files.

My next question: what is the best way for me to write an array I generated
to a file?
And what is the best way for me to load that array again, the next time I
start up my computer?

Basically I am doing very large computations and want to store the results.

Thanks a lot guys!

Jon




On Fri, Mar 18, 2011 at 4:18 PM, Dan Stromberg  wrote:

>
> Are you on windows?
>
> You probably should use / as your directory separator in Python, not \.  In
> Python, and most other programming languages, \ starts an escape sequence,
> so to introduce a literal \, you either need to prefix your string with r
> (r"\foo\bar") or double your backslashes ("\\foo\\bar").
>
> / works fine on windows, and doesn't require escaping ("/foo/bar").
>
> On Fri, Mar 18, 2011 at 2:56 PM, Jon Herman  wrote:
>
>> Jack,
>>
>> thanks.
>>
>> Alright, so what I did is create a file called hello.txt with a single
>> line of text in there. I then did the following:
>>
>> f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
>> full directory on my computer)
>> open("f", "w")
>>
>> And I get the following error: IOError: [Errno 13] Permission denied: 'f'
>> If I open to read, I get: IOError: [Errno 2] No such file or directory:
>> 'f'
>>
>> Can anyone explain to me why this happens?
>>
>>
>>
>>
>>
>> On Fri, Mar 18, 2011 at 3:50 PM, Jack Trades 
>> wrote:
>>
>>>
>>> On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman wrote:
>>>
 Hello all,

 I am pretty new to Python and am trying to write data to a file.
 However, I seem to be misunderstanding how to do so. For starters, I'm not
 even sure where Python is looking for these files or storing them. The
 directories I have added to my PYTHONPATH variable (where I import modules
 from succesfully) does not appear to be it.

 So my question is: How do I tell Python where to look for opening files,
 and where to store new files?

 Thanks,

 Jon


>>> By default Python will read and write files from the directory that your
>>> program is run from.  This cannot always be relied upon though (for instance
>>> if your program was imported as a module from another program).
>>>
>>> To find out what directory your program is currently in use os.getcwd().
>>> Here's an example I just ran...
>>>
>>> >>> import os
>>> >>> os.getcwd()
>>> '/media/DATA/code/lispy/liSpy'
>>>
>>> The folder that is returned from os.getcwd() is the folder that "open"
>>> will use.  You can specify another folder by giving the full path.
>>>
>>> open("/full/path/to/file.txt", "w")
>>>
>>> PYTHONPATH is for importing modules, which is a separate concern.
>>>
>>> --
>>> Jack Trades
>>> Pointless Programming Blog 
>>>
>>>
>>
>> --
>>
>> http://mail.python.org/mailman/listinfo/python-list
>>
>>
>
-- 
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Re: Reading/Writing files

[Jack Trades]

On Fri, Mar 18, 2011 at 5:21 PM, Jon Herman  wrote:

> Folks,
>
> thanks for the many responses! Specifying the full file name (and not using
> parentheses when inappropriate, thanks Jack :)) I am now happily
> reading/writing files.
>
> My next question: what is the best way for me to write an array I generated
> to a file?
> And what is the best way for me to load that array again, the next time I
> start up my computer?
>
> Basically I am doing very large computations and want to store the results.
>
> Thanks a lot guys!
>
> Jon
>
>
To save a data structure like an array (called a list in Python), you can
use the pickle module.  Here's the documentation on pickle.

http://docs.python.org/library/pickle.html
http://www.developertutorials.com/tutorials/python/python-persistence-management-050405-1306/


-- 
Jack Trades
Pointless Programming Blog 
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Re: Use cookies from a script in a browser

[gervaz]

On 18 Mar, 22:52, Miki Tebeka  wrote:
> You can use mechanize, which holds a cookie jar and can user the browser 
> cookies as well.

I use:
opener =
urllib.request.build_opener(urllib.request.HTTPCookieProcessor())
urllib.request.install_opener(opener)
I start scraping from http://page.com/home.html that need the cookies
enabled, then, once I found what I was looking for, I've got
http://page.com/pageX.html and http://page.com/pageY.html. Those page
cannot be viewed if I just copy & paste the url in the browser,
because they need the cookies.

What can I do?

Thanks,
Mattia
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Re: Reading/Writing files

[Westley Martínez]

On Fri, 2011-03-18 at 15:56 -0600, Jon Herman wrote:
> Jack,
> 
> thanks.
> 
> Alright, so what I did is create a file called hello.txt with a single
> line of text in there. I then did the following:
> 
> f="fulldirectory\hello.txt" (where fulldirectory is of course the
> actual full directory on my computer)
> open("f", "w")
> 
> And I get the following error: IOError: [Errno 13] Permission denied:
> 'f'
> If I open to read, I get: IOError: [Errno 2] No such file or
> directory: 'f'
> 
> Can anyone explain to me why this happens?
> 
> 
> 
> 
> On Fri, Mar 18, 2011 at 3:50 PM, Jack Trades
>  wrote:
> 
> 
> On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman
>  wrote:
> Hello all,
> 
> I am pretty new to Python and am trying to write data
> to a file. However, I seem to be misunderstanding how
> to do so. For starters, I'm not even sure where Python
> is looking for these files or storing them. The
> directories I have added to my PYTHONPATH variable
> (where I import modules from succesfully) does not
> appear to be it.
> 
> So my question is: How do I tell Python where to look
> for opening files, and where to store new files?
> 
> Thanks,
> 
> Jon
> 
> 
> 
> By default Python will read and write files from the directory
> that your program is run from.  This cannot always be relied
> upon though (for instance if your program was imported as a
> module from another program).
> 
> To find out what directory your program is currently in use
> os.getcwd().  Here's an example I just ran...
> 
> >>> import os
> >>> os.getcwd()
> '/media/DATA/code/lispy/liSpy'
> 
> The folder that is returned from os.getcwd() is the folder
> that "open" will use.  You can specify another folder by
> giving the full path.
> 
> open("/full/path/to/file.txt", "w")
> 
> PYTHONPATH is for importing modules, which is a separate
> concern.
> 
> -- 
> Jack Trades
> Pointless Programming Blog
> 
> 
Don't put f in quotes. That would just make the string literal 'f'.

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Re: Bounds checking

[Martin De Kauwe]

> Don't check for bounds, fix any bug in the code that would set your
> values out of bounds and use asserts while debugging.
>

whilst that is a nice idea in practice this just is not a practical
solution.


> Otherwise if you really need dynamic checks, it will cost you cpu, for
> sure.

Yes I agree and I hadn't decided whether to add it or not as there
aren't any current issues. However I can see that the check would
overall be safer. I was just wondering if there was some super smartie
pants solution :P


Howeverver you could for instance override the __setatttr__ of
> state object, and call the attribute's associated function.
>
> class State(object):
>     funcTable = {
>        'foo': lambda x: x >= 0.0
>     }
>
>     def __init__(self):
>        self.foo = 0
>
>     def __setattr__(self, attribute, value):
>        if not self.funcTable.get(attribute, lambda x: True)(value):
>            sys.exit('error out of bound')
>        return object.__setattr(self, attribute, value)
>
> Untested, however it's just an idea. I'm not even sure that would be
> less cpu consuming :D

thanks I will look at what you suggested.


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Re: Bounds checking

[Martin De Kauwe]

> Offhand, my only quibble is that sys.exit is not helpful for debugging.  
> Much better to raise an error:
>
>         if not self.funcTable.get(attribute, lambda x: True)(value):
>             raise ValueError ('error out of bound')
>
> or define a subclass of ValueError just for this purpose.  On error, the
> program will stop just as dead, but you'll get a trace.
>
>         Mel.

I think generally I prefer my code to die and as long as I know where
(from the statement) the error occurred I know generally what point I
have to debug up until. Can you explain how your solution would be
easier with a trace as I don't tend to use the raise/assert
functionality so I am interested.

thanks
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Re: ctypes pointer to structure memory swap

[Nobody]

On Fri, 18 Mar 2011 15:16:40 -0700, Wanderer wrote:

> Thanks for the reply, but I'm still not sure I understand. Why should
> Object1 be at address1 and Object2 be at address2 and the next moment
> Object2 is at address1 and Object1 is at address2? I'll try casting
> them to see what the value is before and after calling
> ReleaseCameraSettingStruct.

QCamSettingsEx is a ctypes Struct object. The pSettingsID "field" is a
ctypes field, not a Python field. It will contain a "bare" pointer to the
C-struct for the QCamSettingId object.

The point of a ctypes Struct is to store data in a format usable by C
code, i.e. the memory layout will match that of a C struct. In particular,
pointers within that struct will be pointers to C-compatible data (e.g. C
structs), not pointers to Python objects. If you access the fields from
Python, ctypes will generate Python objects on-the-fly from the raw data.

Whenever you read the pSettingsID field, ctypes will generate a ctypes
pointer object (LP_QCamSettingId?) which wraps the underlying C pointer.
If you dereference that, ctypes will generate a Python QCamSettingId
object which wraps the C struct.

As you aren't storing the references, as soon as the print statement
completes, the reference count will drop to zero and the object will be
deallocated. The next time you reference pSettingsID or pSettingsID[0], a
new object will be constructed. The addresses (and thus IDs) of the Python
objects are entirely arbitrary.

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Re: Reading/Writing files

[Ethan Furman]

Dan Stromberg wrote:


Are you on windows?

You probably should use / as your directory separator in Python, not \.  
In Python, and most other programming languages, \ starts an escape 
sequence, so to introduce a literal \, you either need to prefix your 
string with r (r"\foo\bar") or double your backslashes ("\\foo\\bar").


/ works fine on windows, and doesn't require escaping ("/foo/bar").


Depends on your definition of 'fine'.

--> from glob import glob
--> from pprint import pprint as pp
--> pp(glob('c:/temp/*.pdf'))
['c:/temp\\choose_python.pdf',
 'c:/temp\\COA.pdf',
 'c:/temp\\job_setup.pdf']

Visually ugly, and a pain to compare files and paths.

~Ethan~

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Re: Reading/Writing files

[Westley Martínez]

On Fri, 2011-03-18 at 15:18 -0700, Dan Stromberg wrote:
> 
> Are you on windows?
> 
> 

You shouldn't use / or \ on Windows. You should use os.path.join(). On
Windows, when you start mixing / with \\ and spaces things can get hairy
and obscure. It's always best to just use os.path.join().








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Re: Bounds checking

[Dan Stromberg]

Actually, I'd probably create a class with 3 arguments - an initial value, a
lower bound, and an upper bound, give it a _check method, and call _check
from the various operator methods.  The class would otherwise impersonate an
int.

In code that isn't performance-critical, it's better to check for errors on
a level that seems excessive to many; this is how I like to program - it
tends to stop bugs in their tracks, rather than allowing them to manifest
somewhere far away, elsewhere in the code,  yielding a potentially
time-consuming bug chase.  So I'll have if's and asserts checking
assumptions everywhere - at the beginning of a callable, at the end, in the
middle - inspired by Eiffel's heavy assumption checking.

Python code doesn't need to be troublesome.  I'm told this is how a famous
chess engine (was it Crafty?) got pretty much all of its bugs out.

Or if things don't need to be in the correct range every step of the way (or
rather, if they must be able to temporarily step outside their bounds), then
you could make self._check() be self.check(), and call it externally on an
as-needed basis instead.

Performance-oriented programming is fun, but not all programming is
performance-oriented, and shouldn't be treated as though it is.

On Fri, Mar 18, 2011 at 7:24 AM, Martin De Kauwe  wrote:

> Hi,
>
> if one has a set of values which should never step outside certain
> bounds (for example if the values were negative then they wouldn't be
> physically meaningful) is there a nice way to bounds check? I
> potentially have 10 or so values I would like to check at the end of
> each iteration. However as the loop is over many years I figured I
> probably want to be as optimal as possible with my check. Any
> thoughts?
>
> e.g. this is my solution
>
> # module contain data
> # e.g. print state.something might produce 4.0
> import state as state
>
> def main():
>for i in xrange(num_days):
># do stuff
>
># bounds check at end of iteration
>bounds_check(state)
>
>
> def bounds_check(state):
>""" check state values are > 0 """
>for attr in dir(state):
>if not attr.startswith('__') and getattr(state, attr) < 0.0:
>print "Error state values < 0: %s" % (attr)
>sys.exit()
>
> if __name__ == "__main__":
>sys.exit(main())
>
> thanks
>
> Martin
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Reading/Writing files

[Jon Herman]

Wow, Jack, that is one awesome and simple module...thank you so much! I am
happily storing and accessing all the arrays I could ever want :)

Thanks to all for the quick assistance!




On Fri, Mar 18, 2011 at 4:24 PM, Jack Trades wrote:

>
> On Fri, Mar 18, 2011 at 5:21 PM, Jon Herman  wrote:
>
>> Folks,
>>
>> thanks for the many responses! Specifying the full file name (and not
>> using parentheses when inappropriate, thanks Jack :)) I am now happily
>> reading/writing files.
>>
>> My next question: what is the best way for me to write an array I
>> generated to a file?
>> And what is the best way for me to load that array again, the next time I
>> start up my computer?
>>
>> Basically I am doing very large computations and want to store the
>> results.
>>
>> Thanks a lot guys!
>>
>> Jon
>>
>>
> To save a data structure like an array (called a list in Python), you can
> use the pickle module.  Here's the documentation on pickle.
>
> http://docs.python.org/library/pickle.html
>
> http://www.developertutorials.com/tutorials/python/python-persistence-management-050405-1306/
>
>
>
> --
> Jack Trades
> Pointless Programming Blog 
>
>
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Re: multiprocessing Pool workers cannot create subprocesses

[Jason Grout]

On 3/18/11 3:29 PM, Ned Deily wrote:

In article<4d838d28.5090...@creativetrax.com>,
  Jason Grout  wrote:

The problem appears to be that multiprocessing sets its workers to have
the daemon flag set to True, which prevents workers from creating child
processes.  If I uncomment the line indicated in the code, I can create
child processes and the program works (it prints out the even numbers
from 0 to 18).

It makes me nervous to just change the daemon status of the process like
that, especially when I don't know the reason the workers have
daemon=True to begin with.  What is the reasoning behind that decision?
   What issues do we need to worry about if we just set the daemon mode
flag like in the above code?


http://docs.python.org/library/multiprocessing.html#multiprocessing.Proce
ss.daemon

"When a process exits, it attempts to terminate all of its daemonic
child processes.

Note that a daemonic process is not allowed to create child processes.
Otherwise a daemonic process would leave its children orphaned if it
gets terminated when its parent process exits. Additionally, these are
not Unix daemons or services, they are normal processes that will be
terminated (and not joined) if non-daemonic processes have exited."



Right; thanks.  Let me rephrase my questions:

1. Why is important that the multiprocessing Pool worker processors have 
daemon=True (I think this is the same as asking: why is it important 
that they be terminated with terminate() rather than join() )?


2. Is it safe for us to reset a Pool worker process to have daemon=False 
before starting a subprocess from that worker, like in the code from the 
original message?


Thanks,

Jason
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SocketServer.BaseRequestHandler has the data, and now?

[ao11]

Hello,

I wrote a test application to play around with UDP, the receiving part
looks like:

class proxyServer(SocketServer.ThreadingMixIn,
SocketServer.UDPServer):
pass

class proxyHandler(SocketServer.BaseRequestHandler):

def handle(self):
data   = self.request[0]
source = self.request[1]
cur_thread = threading.currentThread()
response = "%s - %s: %s" % (cur_thread.getName(), source,
data)
print response

class proxy(process) :

def __init__(self, id, context) :
process.__init__(self, id, context, self.run())
self.server = proxyServer(("", 58889), proxyHandler)
self.thread =
threading.Thread(target=self.server.serve_forever)
self.thread.setDaemon(True)

def __del__(self) :
if self.server != None :
self.server.shutdown()

def run(self) :
self.context.model.register(self)
self.thread.start()
...
...
...

def notify(self) :
print "notify " + str(self.id)

So far so good, but how do I get the data back from the handle method
to somewhere else? In my case I yust would like to add every incoming
datagram to a queue and process it later in a different thread.

How do I hand over the queue to the class
proxyHandler(SocketServer.BaseRequestHandler)?

thanks,

AO
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[J Peyret]

On Mar 18, 2:15 pm, Carl Banks  wrote:

> Multiple people reproduce a Python hang/crash yet it looks like no one
> bothered to submit a bug report
>
> I observed the same behavior (2.6 and 3.2 on Linux, hangs) and went
> ahead and submitted a bug report.
>
> Carl Banks

Speaking for myself, I've only put in one bug report on an OSS
project.  Won't do it again.

Firefox, some kinda "attribute works with html, but blows up on xhtml"
issue.  Nothing that was really xhtml related, but their Bugzilla
folks pulled out some unconvincing RFC crap claiming that it was out
of scope for xhtml as opposed to html so they wouldn't fix it.

Their choice.  4 yrs ago.

Still getting occasional emails from Bugzilla about that "we won't fix
it for you" bug.  At least 2 dozen over the years.  Nothing about
fixing it, just status churn.

If I ever specifically work on an OSS project's codeline, I'll post
bug reports, but frankly that FF example is a complete turn-off to
contributing by reporting bugs.
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[Terry Reedy]

On 3/18/2011 5:15 PM, Carl Banks wrote:


Multiple people reproduce a Python hang/crash yet it looks like no one
bothered to submit a bug report


I did not because I did not initially see a problem...


I observed the same behavior (2.6 and 3.2 on Linux, hangs) and went
ahead and submitted a bug report.


http://bugs.python.org/issue11603

where I added additional comments.

--
Terry Jan Reedy

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Re: Reading/Writing files

[Dan Stromberg]

On Fri, Mar 18, 2011 at 4:00 PM, Ethan Furman  wrote:

> Dan Stromberg wrote:
>
>>
>> Are you on windows?
>>
>> You probably should use / as your directory separator in Python, not \.
>>  In Python, and most other programming languages, \ starts an escape
>> sequence, so to introduce a literal \, you either need to prefix your string
>> with r (r"\foo\bar") or double your backslashes ("\\foo\\bar").
>>
>> / works fine on windows, and doesn't require escaping ("/foo/bar").
>>
>
> Depends on your definition of 'fine'.
>
> --> from glob import glob
> --> from pprint import pprint as pp
> --> pp(glob('c:/temp/*.pdf'))
> ['c:/temp\\choose_python.pdf',
>  'c:/temp\\COA.pdf',
>  'c:/temp\\job_setup.pdf']
>
> Visually ugly, and a pain to compare files and paths.
>

I argue that the first is quite a bit more readable than the second:
   'c:/temp/choose_python.pdf'
   os.path.join([ 'c:', 'temp', 'choose_python.pdf' ])

Also, heard of os.path.normpath?  You probably shouldn't compare pathnames
without it.
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[Carl Banks]

On Mar 18, 5:31 pm, J Peyret  wrote:
> If I ever specifically work on an OSS project's codeline, I'll post
> bug reports, but frankly that FF example is a complete turn-off to
> contributing by reporting bugs.

You probably shouldn't take it so personally if they don't agree with
you.  But it's ok, it's not unreasonable to call attention to (actual)
bugs here.

I was surprised, though, when several people confirmed but no one
reported it, especially since it was a crash, which is quite a rare
thing to find.  (You should feel proud.)


Carl Banks
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Re: class error

[Terry Reedy]

On 3/18/2011 5:27 PM, monkeys paw wrote:

TypeError: Error when calling the metaclass bases
module.__init__() takes at most 2 arguments (3 given)

OK, i overlooked that and the error was not very enlightening.


A detailed explanation: every module is an instance of a class we will 
call Module. Every class is an instance of some class, its metaclass. 
The default metaclass, in the absence of any indication otherwise, is 
class type. So your class statement was translated to


type('FileInfo',(UserDict,), d)
where d is a dict mappint '__init__' to the function object.

type.__new__ checks the types (metaclasses) of each of the base classes. 
In particular, it sees that type(UxerDict) is Module, not type. Since it 
assumed that UserDict is a class (since you said it was), it assumed 
that Module is a proper metaclass and called

  Module('FileInfo',(UserDict,), d)
But Module is not a metaclass and does not expect the tuple of base 
classes, and Module.__new__ passed too much to Module.__init__.


Since others have made the same mistake, I opened an issue to improve 
the message.

http://bugs.python.org/issue11604

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Re: Bounds checking

[Terry Reedy]

On 3/18/2011 10:24 AM, Martin De Kauwe wrote:


def bounds_check(state):
 """ check state values are>  0 """
 for attr in dir(state):
 if not attr.startswith('__') and getattr(state, attr)<  0.0:
 print "Error state values<  0: %s" % (attr)


dir() has to do a bit a computation. I would be tempted to give 'state' 
a set of attributes to check. Call it 'nonnegatives'.

   for attr in nonnegatives:
  if ...

This allows for attributes not subject to that check.

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How to install python xlwt in ubuntu 9

[ratna PB]

Hey friends i tried a lot to unstall excel xlwt in ubuntu 9 but failed
please help me before i get full fraustrated...
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Syntax Error

[Manatee]

I hope this is the place to post this question. I am a really new
pythonista. I am studying Tkinter and when I run this basic code, I
get  a syntax error on line 20,  print "hi there, everyone". Its a
simple print line, but I can't see the problem. I am using Python
2.71, gVim for an editor, and a console window to execute the program.
Here is the link to the website that I am trying to follow:

http://www.pythonware.com/library/tkinter/introduction/hello-again.htm

Thanks for any help.


# File: hello2.py

from Tkinter import *

class App:

def __init__(self, master):

frame = Frame(master)
frame.pack()

self.button = Button(frame, text="QUIT", fg="red",
command=frame.quit)
self.button.pack(side=LEFT)

self.hi_there = Button(frame, text="Hello",
command=self.say_hi)
self.hi_there.pack(side=LEFT)

def say_hi(self):

print "hi there, everyone"

root = Tk()

app = App(root)

root.mainloop()
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Re: Syntax Error

[xDog Walker]

On Friday 2011 March 18 21:39, Manatee wrote:
> I hope this is the place to post this question. I am a really new
> pythonista. I am studying Tkinter and when I run this basic code, I
> get  a syntax error on line 20,  print "hi there, everyone". Its a
> simple print line, but I can't see the problem. I am using Python
> 2.71, gVim for an editor, and a console window to execute the program.
> Here is the link to the website that I am trying to follow:
>
> http://www.pythonware.com/library/tkinter/introduction/hello-again.htm
>
> Thanks for any help.
>
>
> # File: hello2.py
>
> from Tkinter import *
>
> class App:
>
> def __init__(self, master):
>
> frame = Frame(master)
> frame.pack()
>
> self.button = Button(frame, text="QUIT", fg="red",
> command=frame.quit)
> self.button.pack(side=LEFT)
>
> self.hi_there = Button(frame, text="Hello",
> command=self.say_hi)
> self.hi_there.pack(side=LEFT)
>
> def say_hi(self):
>
> print "hi there, everyone"
>
> root = Tk()
>
> app = App(root)
>
> root.mainloop()

Post the complete traceback.

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Re: Syntax Error

[Thomas L. Shinnick]

At 11:39 PM 3/18/2011, Manatee wrote:

I hope this is the place to post this question. I am a really new
pythonista. I am studying Tkinter and when I run this basic code, I
get  a syntax error on line 20,  print "hi there, everyone". Its a
simple print line, but I can't see the problem. I am using Python
2.71, gVim for an editor, and a console window to execute the program.
Here is the link to the website that I am trying to follow:

http://www.pythonware.com/library/tkinter/introduction/hello-again.htm

Thanks for any help.


No help, really, but copy-n-paste of the below ran fine first time on 
2.7 install on Win7.  Maybe accidental special characters in source 
file?  How about you also try copy-n-paste from your email?  Who knows  :-)



# File: hello2.py

from Tkinter import *

class App:

def __init__(self, master):

frame = Frame(master)
frame.pack()

self.button = Button(frame, text="QUIT", fg="red",
command=frame.quit)
self.button.pack(side=LEFT)

self.hi_there = Button(frame, text="Hello",
command=self.say_hi)
self.hi_there.pack(side=LEFT)

def say_hi(self):

print "hi there, everyone"

root = Tk()

app = App(root)

root.mainloop()
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Re: Syntax Error

[Vlastimil Brom]

2011/3/19 Manatee :
> I hope this is the place to post this question. I am a really new
> pythonista. I am studying Tkinter and when I run this basic code, I
> get  a syntax error on line 20,  print "hi there, everyone". Its a
> simple print line, but I can't see the problem. I am using Python
> 2.71, gVim for an editor, and a console window to execute the program.
> Here is the link to the website that I am trying to follow:
>
> http://www.pythonware.com/library/tkinter/introduction/hello-again.htm
>
> Thanks for any help.
>
> [...]

Hi,
the code on the mentioned page as well as yours (with adapted
indentation and wordwrapping from the mail) seems ok for python 2.

Is it possible, that you are actually using python3?
This would give something like
print "hi there, everyone!"
  ^
SyntaxError: invalid syntax

as print was changed to a funcion in this version.
print("hi there, everyone!")

hth,
 vbr
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Re: Abend with cls.__repr__ = cls.__str__ on Windows.

[J Peyret]

On Mar 18, 6:55 pm, Carl Banks  wrote:
> On Mar 18, 5:31 pm, J Peyret  wrote:
>
> > If I ever specifically work on an OSS project's codeline, I'll post
> > bug reports, but frankly that FF example is a complete turn-off to
> > contributing by reporting bugs.
>
> You probably shouldn't take it so personally if they don't agree with
> you.  But it's ok, it's not unreasonable to call attention to (actual)
> bugs here.
>

No, I didn't take the refusal personally at all, though it seemed
kinda glib to xhtml-not-hmtl out of a bug.  Such is life.

What I object to is getting auto-spammed for years after that because
I was silly enough to enter my email on their database and then being
notified about every single event on that bug.

> I was surprised, though, when several people confirmed but no one
> reported it, especially since it was a crash, which is quite a rare
> thing to find.  (You should feel proud.)
>
> Carl Banks

Yes, that's why I reported it.  Python is extremely stable so it
seemed worthwhile.  And I figured someone on the list would know its
bug quotient.

Impressed that there is already a bit of a proposed approach on the
entry to fix it, you guys are great.

But... I rather thought __repr__ was going to disappear in 3.x, with
just __str__ sticking around.
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Re: Syntax Error

[Terry Reedy]

On 3/19/2011 1:03 AM, Vlastimil Brom wrote:

2011/3/19 Manatee:

I hope this is the place to post this question.


Yes.
Lesson 1. Report Python version used, as things change. For anything 
that seems like it might by os/system specific, include that too.

Lesson 2. Always include tracebacks when there is one.


I am a really new
pythonista. I am studying Tkinter and when I run this basic code, I
get  a syntax error on line 20,  print "hi there, everyone". Its a
simple print line, but I can't see the problem. I am using Python
2.71, gVim for an editor, and a console window to execute the program.
Here is the link to the website that I am trying to follow:

http://www.pythonware.com/library/tkinter/introduction/hello-again.htm

Thanks for any help.

[...]


Hi,
the code on the mentioned page as well as yours (with adapted
indentation and wordwrapping from the mail) seems ok for python 2.

Is it possible, that you are actually using python3?
This would give something like
 print "hi there, everyone!"
   ^
SyntaxError: invalid syntax

as print was changed to a funcion in this version.
print("hi there, everyone!")


If running with Py3, 'import Tkinter' will fail; change to 'import tkinter'.


--
Terry Jan Reedy

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install excel xlwt in ubuntu 9

[ratna PB]

Hey friends i tried a lot to install excel xlwt in ubuntu 9 but
failed
please help me before i get full fraustrated...
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