🌐 Mailman 3 July 2008 - Python-list - python.org

decorators tutorials
by james_027 March 23, 2009

March 23, 2009

Hi, I am learning python by learning django, and I stumble upon decorator which is very cool, any beginners resources for python decorators, although I can google it, I just want to get a good tutorial for this topic. Thanks james

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Re: Implementaion of random.shuffle
by Hrvoje Niksic Feb. 20, 2009

Feb. 20, 2009

Steve Holden <steve(a)holdenweb.com> writes: > So it would appear that the developers chose the Knuth algorithm > (with a slight variation) for *their* implementation. Now you have > to ask yourself whether your surmise is genuinely correct (in which > case the documentation may contain a bug) or whether the > documentation is indeed correct and you are in error. That is a good question. The random module uses the Mersenne twister, which has a repetition period of 2**19937. The number of n-sized permutations of a list with n elements is n!, while each shuffle requires n calls to the PRNG. This means that to be able to generate all permutations, the PRNG must have a period of at least n! * n. In the case of MT, it means that, regarding the period, you are safe for lists with around 2079 elements. shuffle's documentation may have been written before the random module was converted to use the MT. 2**19937 being a really huge number, it's impossible to exhaust the Mersenne twister by running it in sequence. However, there is also the question of the spread of the first shuffle. Ideally we'd want any shuffle, including the first one, to be able to produce any of the n! permutations. To achieve that, the initial state of the PRNG must be able to support at least n! different outcomes, which means that the PRNG must be seeded by at least log2(n!) bits of randomness from an outside source. For reference, Linux's /dev/random stops blocking when 64 bits of randomness are available from the entropy pool, which means that, in the worst case, shuffling more than 20 elements cannot represent all permutations in the first shuffle!

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is it possible to add a property to an instance?
by Darren Dale Feb. 20, 2009

Feb. 20, 2009

Does anyone know if it is possible to add a property to an instance at runtime? I didn't see anything about it in the standard library's new module, google hasn't turned up much either. Thanks, Darren

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PyQt, Cannot send events to objects owned by a different thread?
by Alexander Tuchacek Jan. 18, 2009

Jan. 18, 2009

hallo, i try to adress an qt object self.statusbar.showMessage("rtt %s...." % (n.rtt)) in an callback function, comming from a shared lib importet by ctypes, on osx this works wonderfull when i run the same code on linux (ubuntu gutsy), i get this core dump, ok, i understand that the problem is, that i cant speak to the qt thread, but why does it work on osx? shall i recompile python? pyqt or sip? without threads? could somebody give me a hint what to do best? how can i call a qt object in an c-lib callback? thanks for any help, alex ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread 82c31e8. Receiver 'MainWindow' (of type 'MainWindow') was created in thread 81f5060", file kernel/qcoreapplication.cpp, line 269 Aborted (core dumped)

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using PIL for PCA analysis
by devnew＠gmail.com Jan. 13, 2009

Jan. 13, 2009

hi guys i am trying out PCA analysis using python.I have a set of jpeg(rgbcolor) images whose pixel data i need to extract and make a matrix .( rows =num of images and cols=num of pixels) For this i need to represent an image as an array. i was able to do this using java's BufferedImage as below <javacode> int[] rgbdata = new int[width * height]; image.getRGB(0,0,width,height,rgbdata,0,width); doubles = new double[rgbdata.length]; int i; for ( i = 0; i < bytes.length; i++) { doubles[i] = (double)(rgbdata[i]); } </javacode> this doubles[] now represent a single image's pixels then i can get a matrix of say 4 images ..(each of 4X3 size) <sampledata> images[][] rows=4,cols=12 [ [-4413029.0, -1.0463919E7,... -5201255.0] [-5399916.0, -9411231.0, ... -6583163.0] [-3886937.0, -1.0202292E7,... -6648444.0] [-5597295.0, -7901339.0,... -5989995.0] ] </sampledata> i can normalise the above matrix to zeromean and then find covariance matrix by images * transpose(images) my problem is how i can use PIL to do the same thing..if i extract imagedata using im.getdata() i will get <sampledata> [ [(188, 169, 155), (96, 85, 81),.. (176, 162, 153)] [(173, 154, 148), (112, 101, 97),.. (155, 140, 133)] [(196, 176, 167), (100, 83, 76), ... (154, 141, 132)] [(170, 151, 145), (135, 111, 101), ... (164, 153, 149)] ] </sampledata> i donot know how to find covariance matrix from such a matrix..it would'v been ideal if they were single values instead of tuples..i can't use greyscale images since the unput images are all rgb jpeg can someone suggest a solution? thanks dn

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online money earnings
by dasasdfd Dec. 27, 2008

Dec. 27, 2008

online money earnings value of money money is the life http://moneylife0123.blogspot.com/

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Module for creating a screenshot of a web page given a URL?
by dananrg＠yahoo.com Oct. 23, 2008

Oct. 23, 2008

Is there a Python module that, given a URL, will grab a screenshot of the web page it goes to? I'd like to be able to feed such a module a list of URLs from a file. Thanks very much.

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Snapshot+Clipboard
by Yves Lange Oct. 23, 2008

Oct. 23, 2008

Hello, i'm searching a method to take a snapshot and save it in a jpg, bmp or gif file. I tried with win32api and win32con but it save the snapshot to the clipboard, so i tried to redirect this in a file but i have some problems while getting the IMAGE stocked in the clipboard and save it to a file. Can somebody help me ? Questions: -How can i read the snapshot in the clipboard ? -How can i take a snapshot in a different way (less difficult) ? Thks.

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do you fail at FizzBuzz? simple prog test
by globalrev Oct. 3, 2008

Oct. 3, 2008

http://reddit.com/r/programming/info/18td4/comments claims people take a lot of time to write a simple program like this: "Write a program that prints the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz". for i in range(1,101): if i%3 == 0 and i%5 != 0: print "Fizz" elif i%5 == 0 and i%3 != 0: print "Buzz" elif i%5 == 0 and i%3 == 0: print "FizzBuzz" else: print i is there a better way than my solution? is mine ok?

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tkinter for my python program !!
by karthikbalaguru Sept. 14, 2008

Sept. 14, 2008

Hi, One of my python program needs tkinter to be installed to run successfully. I am using Redhat 9.0 and hence tried installing by copying the tkinter-2.2.2-36.i386.rpm alone from the CD 3 to my pc. But, it is not getting installed and is failing by throwing the below errors. Should i need to configure / install any specific files for resolving this issue ? [root@localhost karthik]# rpm -ivh tkinter-2.2.2-26.i386.rpm warning: tkinter-2.2.2-26.i386.rpm: Header V3 DSA signature: NOKEY, key ID db42a 60e error: Failed dependencies: libtcl8.3.so is needed by tkinter-2.2.2-26.i386 libtix8.1.8.3.so is needed by tkinter-2.2.2-26.i386 libtk8.3.so is needed by tkinter-2.2.2-26.i386 Any ideas ? Thx in advans, Karthik Balaguru

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