Re: [Tutor] Q about .join() Thanks!
Danny Yoo wrote:
> Moreover, most implementations *deliberately* randomize their iteration
> order to avoid a particular kind of hash collision attack out there in
> the wild. See:
In CPython the hash() of a string may change between different runs to fend
off hash collision attacks, but that does not necessarily change the order
of iteration:
In Python 3.4 for example both order and hash value change
$ python3.4 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
-1599197652882818545 baz bar foo
$ python3.4 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
-7773300350121034240 foo bar baz
$ python3.4 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
4096077922251392823 baz bar foo
In Python 3.6 on the other side the hash values still change, but
(insertion) order is preserved:
$ python3.6 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
22453670082131454 foo bar baz
$ python3.6 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
4601604916521659267 foo bar baz
$ python3.6 -c 'd = dict.fromkeys("foo bar baz".split()); print(hash("foo"),
*d)'
5190466601789110813 foo bar baz
So if the OP had used Python 3.6 she would have seen the behaviour she
expected. However, quoting
"""
The order-preserving aspect of this new [dict] implementation is considered
an implementation detail and should not be relied upon
"""
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[Tutor] NameError: name 'hurst' is not defined
Hi. Not sure why this code produces the error like this. This error appears
when i run the code of print "Hurst(GBM): %s" % hurst(gbm):
Traceback (most recent call last): File "", line 1, in
print "Hurst(GBM): %s" % hurst(gbm)NameError: name 'hurst' is not defined
Here is the full code:>>> import statsmodels.tsa.stattools as ts
>>> import urllib>>> from datetime import datetime>>> from pandas_datareader
>>> import data, wb>>> from pandas_datareader.data import DataReader>>> goog =
>>> DataReader("GOOG", "yahoo", datetime(2000,1,1), datetime(2017,1,1))>>>
>>> ts.adfuller(goog['Adj Close'], 1>>> import numpy as np
>>> from numpy import cumsum, log, polyfit, sqrt, std, subtract>>> from
>>> numpy.random import randn>>> def hurst(ts): lags = range(2, 100) tau =
>>> [np.sqrt(std(subtract(ts[lag:], ts[:-lag]))) for lag in lags] poly =
>>> np.polyfit(log(lags), log(tau), 1) return poly[0]*2.0>>> gbm =
>>> log(cumsum(randn(10))+1000)>>> mr = log(randn(10)+1000)>>> tr =
>>> log(cumsum(randn(10)+1)+1000)>>> print "Hurst(GBM): %s" % hurst(gbm)
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Re: [Tutor] Q about .join() Thanks!
>I find out that the outcome for using .join() on a dictionary is totally
>different than it using on list or string. for example,
> >>> seq4 = {'hello':1,'good':2,'boy':3,'doiido':4}
> >>>
> boy:good:doiido:hello
>So my question is why the outcome doesn't show sequentially as the same
>sequence of the original seq4? What pattern do those "keys" of the dictionary
>in the outcome show ?
Dictionaries are not an ordered sequence.
In order to do that you need to create and OrderedDict (in collections)
Modern Dictionaries --> https://www.youtube.com/watch?v=p33CVV29OG8
The mighty Dictionary --> https://www.youtube.com/watch?v=C4Kc8xzcA68&t=142s
This email is confidential and may be subject to privilege. If you are not the
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Re: [Tutor] NameError: name 'hurst' is not defined
On 14/02/17 01:55, Allan Tanaka via Tutor wrote:
> Hi. Not sure why this code produces the error like this. This error appears
> when i run the code of print "Hurst(GBM): %s" % hurst(gbm):
> Traceback (most recent call last): File "", line 1, in
> print "Hurst(GBM): %s" % hurst(gbm)NameError: name 'hurst' is not defined
>
> Here is the full code:>>> import statsmodels.tsa.stattools as ts
import urllib>>> from datetime import datetime>>> from pandas_datareader
import data, wb>>> from pandas_datareader.data import DataReader>>> goog =
DataReader("GOOG", "yahoo", datetime(2000,1,1), datetime(2017,1,1))>>>
ts.adfuller(goog['Adj Close'], 1>>> import numpy as np
from numpy import cumsum, log, polyfit, sqrt, std, subtract>>> from
numpy.random import randn>>> def hurst(ts): lags = range(2, 100) tau =
[np.sqrt(std(subtract(ts[lag:], ts[:-lag]))) for lag in lags] poly =
np.polyfit(log(lags), log(tau), 1) return poly[0]*2.0>>> gbm =
log(cumsum(randn(10))+1000)>>> mr = log(randn(10)+1000)>>> tr =
log(cumsum(randn(10)+1)+1000)>>> print "Hurst(GBM): %s" % hurst(gbm)
The mail system has mangled your code, you need to post
in plain text to preserve layout. I'll try to reconstruct
it based on >>> as the interpreter prompt:
>>> import urllib
>>> from datetime import datetime
>>> from pandas_datareader import data, wb
>>> from pandas_datareader.data import DataReader
>>> goog = DataReader("GOOG", "yahoo", datetime(2000,1,1),
datetime(2017,1,1))
>>> ts.adfuller(goog['Adj Close'], 1
there seems to be a missing closing paren here?
Also where does 'ts' come from, its not defined above?
>>> import numpy as np
>>> from numpy import cumsum, log, polyfit, sqrt, std, subtract
>>> from numpy.random import randn
>>> def hurst(ts):
lags = range(2, 100)
tau = [np.sqrt(std(subtract(ts[lag:], ts[:-lag])))
for lag in lags]
poly = np.polyfit(log(lags), log(tau), 1)
return poly[0]*2.0
>>> gbm = log(cumsum(randn(10))+1000)
>>> mr = log(randn(10)+1000)
>>> tr = log(cumsum(randn(10)+1)+1000)
>>> print "Hurst(GBM): %s" % hurst(gbm)
Is that right?
Apart from the missing ')' and undefined ts, it looks OK.
Have you tried putting it into a file and running it
as a script? That will avoid risk of pollution from
any previous context in the interpreter.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: [Tutor] NameError: name 'hurst' is not defined
Allan Tanaka via Tutor wrote:
> Hi. Not sure why this code produces the error like this. This error
> appears when i run the code of print "Hurst(GBM): %s" % hurst(gbm):
> Traceback (most recent call last): File "", line 1, in
> print "Hurst(GBM): %s" % hurst(gbm)NameError: name 'hurst'
> is not defined
>
> Here is the full code:>>> import statsmodels.tsa.stattools as ts
import urllib>>> from datetime import datetime>>> from
pandas_datareader import data, wb>>> from pandas_datareader.data import
DataReader>>> goog = DataReader("GOOG", "yahoo", datetime(2000,1,1),
datetime(2017,1,1))>>> ts.adfuller(goog['Adj Close'], 1>>> import numpy
as np from numpy import cumsum, log, polyfit, sqrt, std, subtract>>>
from numpy.random import randn>>> def hurst(ts): lags = range(2, 100)
tau = [np.sqrt(std(subtract(ts[lag:], ts[:-lag]))) for lag in lags]
poly = np.polyfit(log(lags), log(tau), 1) return poly[0]*2.0>>> gbm =
log(cumsum(randn(10))+1000)>>> mr = log(randn(10)+1000)>>> tr =
log(cumsum(randn(10)+1)+1000)>>> print "Hurst(GBM): %s" %
hurst(gbm)
See that mess? You need to check your mail client. When I undo the
scrambling...
$ cat hurst.py
import statsmodels.tsa.stattools as ts
import urllib
from datetime import datetime
from pandas_datareader import data, wb
from pandas_datareader.data import DataReader
goog = DataReader("GOOG", "yahoo", datetime(2000,1,1), datetime(2017,1,1))
ts.adfuller(goog['Adj Close'], 1)
import numpy as np
from numpy import cumsum, log, polyfit, sqrt, std, subtract
from numpy.random import randn
def hurst(ts):
lags = range(2, 100)
tau = [np.sqrt(std(subtract(ts[lag:], ts[:-lag]))) for lag in lags]
poly = np.polyfit(log(lags), log(tau), 1)
return poly[0]*2.0
gbm = log(cumsum(randn(10))+1000)
mr = log(randn(10)+1000)
tr = log(cumsum(randn(10)+1)+1000)
print "Hurst(GBM): %s" % hurst(gbm)
...the code runs without error:
$ python hurst.py
Hurst(GBM): 0.502272832664
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Re: [Tutor] NameError: name 'hurst' is not defined
On 14/02/17 10:11, Alan Gauld via Tutor wrote: ts.adfuller(goog['Adj Close'], 1 > > there seems to be a missing closing paren here? > Also where does 'ts' come from, its not defined above? Ah! I see from Peters post that I missed the first line of code. But I still see a missing ')'... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Exponential function
Hi For the function 1*10^x, is there a specific way of computing *10^x or will it just be the following : 1*10**x Thank you. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Tutor Digest, Vol 156, Issue 33
Please l will like to have a mentor how can I have it
On Feb 14, 2017 09:53, wrote:
> Send Tutor mailing list submissions to
> tutor@python.org
>
> To subscribe or unsubscribe via the World Wide Web, visit
> https://mail.python.org/mailman/listinfo/tutor
> or, via email, send a message with subject or body 'help' to
> tutor-requ...@python.org
>
> You can reach the person managing the list at
> tutor-ow...@python.org
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Tutor digest..."
>
> Today's Topics:
>
>1. Re: Access a .tcl file in python (Alan Gauld)
>2. Re: Q about .join() Thanks! (David Rock)
>3. Re: Fwd: Re: GUI for ANSI colors (Alan Gauld)
>4. Re: Q about .join() Thanks! (Alan Gauld)
>5. Re: Q about .join() Thanks! (Danny Yoo)
>6. Re: Q about .join() Thanks! (Peter Otten)
>
>
> -- Forwarded message --
> From: Alan Gauld
> To: tutor@python.org
> Cc:
> Date: Tue, 14 Feb 2017 01:17:39 +
> Subject: Re: [Tutor] Access a .tcl file in python
> On 13/02/17 19:37, Lily ANTONY wrote:
>
> > I have a .tcl file.Does anyone know how to load a .tcl file in to
> python?I
> > need to call the .tcl file in
> > a python program..Thanks!
>
> In general you can't run code for one language in a
> program written in another language. (There are a few
> exceptions, usually where one language is written in
> the other).
>
> The nearest you can usually get is to execute the
> Tcl program using the tcl interpreter (tclsh) from
> the OS using a module like subprocess.
>
> However, Tcl and Python do have a connection via
> the Tkinter module and you can call tcl code
> using Tkinter like so(Python v3):
>
> import tkinter
> tcl = tkinter.Tcl()
> tcl.eval("""
> puts [expr 4+5] # or any other arbitrary tcl
> """)
>
> So to execute a Tcl file you can read the contents
> into a string and then execute that string. Note that
> the return value will always be a string.
>
> HTH
>
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
>
>
>
>
>
> -- Forwarded message --
> From: David Rock
> To: "tutor@python.org"
> Cc:
> Date: Mon, 13 Feb 2017 19:20:52 -0600
> Subject: Re: [Tutor] Q about .join() Thanks!
>
> > On Feb 13, 2017, at 12:34, SIJIA CHEN wrote:
> >
> > I find out that the outcome for using .join() on a dictionary is totally
> different than it using on list or string. for example,
> >
> seq4 = {'hello':1,'good':2,'boy':3,'doiido':4}
> print ':'.join(seq4)
> > boy:good:doiido:hello
> > So my question is why the outcome doesn't show sequentially as the same
> sequence of the original seq4? What pattern do those "keys" of the
> dictionary in the outcome show ?
>
> Dictionaries (in particular, their keys) are unordered. You can not rely
> on them to be in a particular sequence. The reason for this, from a
> practical perspective, is you are expected to ask for the specific key; you
> should not care about the ordering.
>
> Lists, on the other hand, have a specific order by design so will always
> be in the order they were created.
>
> What are you trying to do with join() on a dictionary in the first place?
> Is there a specific outcome you are trying to get? It’s unlikely that
> using join on a dictionary is what you actually want.
>
> —
> David Rock
> da...@graniteweb.com
>
>
>
>
>
>
> -- Forwarded message --
> From: Alan Gauld
> To: tutor@python.org
> Cc:
> Date: Tue, 14 Feb 2017 01:26:45 +
> Subject: Re: [Tutor] Fwd: Re: GUI for ANSI colors
> On 14/02/17 00:58, Alan Gauld forwarded:
>
> > red = '\033[91m'
> > yel = '\033[93m'
> > blu = '\033[34m'
> > grn = '\033[32m'
>
> These are indeed the ANSI codes for the colours but ANSI
> codes only work in an ANSI terminal and GUIs are not
> ANSI terminals. Instead they have their own ideas on
> colours and you need to use those. They all support
> the standard 16 colours used in ANSI however, so in
> your case (for Tkinter at least) just use the names
> 'red', 'yellow', 'blue' and 'green'
>
> > colors = [red, yel, blu, grn]
>
> colors = ['red', 'yellow', 'blue', 'green']
>
>
> > final_word = ''.join(choice(colors) + char for char in word)
>
> But again that won't work in a GUI, you need to use the GUIs
> way of colouring. In Tkinter that's via tags as per my
> previous post, reproduced here).
>
> > ###
> > from Tkinter import *
> >
> > n = 0
> > top = Tk()
> > t = Text(top, width=25, height=2)
> > t.pack()
> >
> > # set up tags for the colors
> > colors = ['red','blue','green']
> > for col in colors:
> > t.tag_config(col, foreground=col)
> >
> > def addWords():
> > n = 0
> > for word in "Hello ", "bright ", "world ":
> > t.insert(END,wo
Re: [Tutor] Exponential function
On 14/02/17 12:03, Aaliyah Ebrahim wrote: > For the function 1*10^x, is there a specific way of computing *10^x or will > it just be the following : > > 1*10**x To compute it if you don't know x in advance then yes, use something like value = 10**x But if you know the value in advance you can write it in a more compact form as: value = 1e5 # or 3e7 or whatever... say(if x=5). Experiment at the interactive prompt to see how it works. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Tutor Digest, Vol 156, Issue 33
As per my offline reply, just send messages to the list and the whole group will act as a virtual mentor. One other thing though. Please start new topics with a new message. Do NOT reply to an existing thread as it messes up the archives. And especially do not reply to a digest message. And use a meaningful subject line. Its very hard to find a question in the archive if the subject is Re: Tutor Digest, Vol 156, Issue 33 or similar. (unless of course you really are asking a question about that particular digest message rather than its content - but if so it should probably go to the list owners.) It's much easier to find a message with a subject like help with python log functions or whatever. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Exponential function
On Tue, Feb 14, 2017 at 11:01 PM, Alan Gauld via Tutor wrote:
> To compute it if you don't know x in advance then yes,
> use something like
>
> value = 10**x
>
> But if you know the value in advance you can write it in
> a more compact form as:
>
> value = 1e5 # or 3e7 or whatever...
10**5 is an int and 1e5 is a float. This could lead to a significant
loss of precision depending on the calculation. For example:
>>> x = 10**5 * 1234567890123456789
>>> y = 1e5 * 1234567890123456789
>>> x - y
16777216.0
Replacing 10**5 with 10 is a compile-time optimization (constant
expression folding), so you needn't worry about manually optimizing
it. For example:
>>> compile('10**5', '', 'exec').co_consts
(10, 5, None, 10)
The compiled bytecode refers to the pre-computed constant:
>>> dis.dis(compile('10**5', '', 'exec'))
1 0 LOAD_CONST 3 (10)
3 POP_TOP
4 LOAD_CONST 2 (None)
7 RETURN_VALUE
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