🌐 Mailman 3 November 2007 - Python-list - python.org

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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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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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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From D
by bearophileHUGS＠lycos.com Sept. 8, 2008

Sept. 8, 2008

There are various things I like about the D language that I think Python too may enjoy. Here are few bits (mostly syntactical ones): 1) (we have discussed part of this in the past) You can put underscores inside number literals, like 1_000_000, the compiler doesn't enforce the position of such underscores, so you can also put them like this: 1_00_000. You can put them in literals of decimals, binary, hex, etc. I think it's quite useful, because when in Python code I have a line like: for i in xrange(1000000): I need some time to count the zeros, because the lower levels of my visual systems can't count/group them quickly (perceptually). While in a syntax like: for i in xrange(1_000_000): my eyes help me group them at once. 2) Base 2 number literals, and base 2 "%b" printing with the writefln. Base-2 numbers are less common in Python code, but once in a while I use them. For example: import std.stdio; void main() { auto x = 0b0100_0011; writefln("%b", x); writefln("%.8b", x); writefln(x); } Prints: 1000011 01000011 67 3) All string literals are multi line. So you can write: a = "how are you"; There's no need for """ """. 4) With D I have created an xsplit() generator, and from my tests it's quite faster than the split(), expecially if the string/lines you want to split are few hundred chars long or more (it's not faster if you want to split very little strings). So I think Python can enjoy such string method too (you can probably simulate an xsplit with a regular expression, but the same is true for some other string methods too). Bye, bearophile

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Building a Python app with Mozilla
by Thorsten Kampe July 14, 2008

July 14, 2008

Hi, I've already sent this to the Komodo mailing list (which seemed to me the more appropriate place) but unfortunately I got no response. I'd like to build a Python GUI app. Neither Tkinter nor Wxpython nor PyQT are actually what I want (because the lack of GUI builders and they don't really look good on Windows and Linux). Komodo itself is an excellent example of a - at least Python driven - application that looks superb and has superior functionality so it seems natural to use the Komodo approach for me. Some questions * Is there a simple How-To how to build a very simple (Python) app with the Mozilla framework? Kind of "Hello world"...? * Is is reasonable to think that building a GUI with Mozilla is easier than using Python frameworks because Mozilla does most of the GUI work? Thorsten

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Problem with PEXPECT in Python
by Kevin Erickson June 4, 2008

June 4, 2008

Hello, I am attempting to use pexpect in python to copy files from a server using scp; the copy works however exceptions are thrown and it exits unsuccessfully. Below is the a sample code and the error: #Begin Code import sys import pexpect def GetServerData(self): foo = pexpect.spawn('scp user@server.com:/home/config/ role{/file1,/files/file2,/files/file3} /tmp') foo.expect('.*password:*') foo.sendline('server_password') foo.interact() #End Code #Begin Output file1 100% 10KB 10.0KB/s 00:01 file2 100% 946 0.9KB/s 00:00 file3 100% 1655 1.6KB/s 00:00 Traceback (most recent call last): File "mygui.py", line 6, in ? f = Form1() File "/home/Kevin/form1.py", line 41, in __init__ self.GetServerData() File "/home/Kevin/form1.py", line 84, in GetServerData foo.interact() File "/usr/lib/python2.4/site-packages/pexpect.py", line 1062, in interact selfw.__interact_copy(escape_character) File "/usr/lib/python2.4/site-packages/pexpect.py", line 1086, in __interact_copy data = self.__interact_read(self.child_fd) File "/usr/lib/python2.4/site-packages/pexpect.py", line 1075, in __interact_read return os.read(fd, 1000) OSError: [Errno 5] Input/output error #End Output The problem seems to be with the call foo.interact(); does anyone know how to fix this? Any help will be much appreciated.

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smtplib "authentication required" error
by carl.reimann＠gmail.com May 17, 2008

May 17, 2008

In using a simple smtp routine: # begin example >>> import smtplib >>> server = smtplib.SMTP('outgoing.verizon.net') >>> server.sendmail('my(a)address.net', 'another(a)address.net', """To: another(a)address.net From: my(a)address.net Subject: Shakespeare Quote Tis like the breath of an unfeed lawyer... """) >>> server.quit() # end example I find the following error: raise SMTPSenderRefused(code, resp, from_addr) smtplib.SMTPSenderRefused: (550, '5.7.1 Authentication Required', 'myuserid(a)verizon.net') I have attempted to incorporate into the interactive session: server.login = ('userid', 'password') # the same ones I use in my email program But I get the same error result. My objective is to have a simple way to send email from the command line. To do this I will write a script which can read in a file and send it to the address on top of the file. What is the procedure for authentication? Using the KMail email program (Linux, KDE desktop), I send mail through my Verizon account. Under the Configure KMail / Accounts / Modify Account / Extras tab, I clicked "Check what the server supports" and it came back 'no encryption' and 'cleartext'. So it doesn't seem that it would involve complex procedures. Any help welcome.

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Why can't timedeltas be divided?
by Dan Bishop April 27, 2008

April 27, 2008

If I try to write something like: num_weeks = time_diff / datetime.timedelta(days=7) I get: TypeError: unsupported operand type(s) for /: 'datetime.timedelta' and 'datetime.timedelta' Of course, one could extend the timedelta class to implement division, def _microseconds(self): return (self.days * 86400 + self.seconds) * 1000000 + self.microseconds def __truediv__(self, other): if isinstance(other, datetime.timedelta): return self._microseconds() / other._microseconds() else: return datetime.timedelta(0, 0, self._microseconds() / other) def __floordiv__(self, other): if isinstance(other, datetime.timedelta): return self._microseconds() // other._microseconds() return NotImplemented but why is a basic arithmetic operation missing from the standard datetime module?

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[ANN] Python courses this Fall
by wesley chun April 1, 2008

April 1, 2008

Folks, I'd like to announce my final Python courses for 2007: Need to get up-to-speed with Python as quickly as possible? Come join me, Wesley Chun, author of Prentice-Hall's well-received "Core Python Programming," for another set of courses this Fall in beautiful Northern California! This will be the final set for 2007... if you miss these, you'll have to wait until next year. I look forward to meeting you! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (COMPREHENSIVE) INTRODUCTION TO PYTHON: Mon-Wed, 2007 Oct 8-10 This is course is meant for those new to Python and/or want to get more in-depth formal training. We will immerse you in the world of Python in only a few days. We will show you more than just its syntax (which you don't really need a book to learn, right?). Knowing more about how Python works under the covers, including the relationship between data objects and memory management, will make you a much more effective Python programmer coming out of the gate. 3 hands-on labs each day will help hammer the concepts home. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - INTERNET PROGRAMMING WITH PYTHON: Sat, 2007 Oct 13 This 1-day course will introduce current Python programmers to 3 distinct areas of Internet programming, each in self-contained modules with a set of lab exercises following each lecture topic: Network Programming using Sockets -- Underneath all of today's network protocols, i.e., HTTP, FTP, RDBMS, IM, e-mail, etc., lies the main communication mechanism, sockets. Here, we introduce client/server architecture and how to program sockets using Python. Internet Client Programming -- One level above the socket layer are well-known Internet protocols such as FTP, NNTP, POP3, and SMTP. In this section, we learn how to create Internet clients of these protocols to transfer files, send and receive e-mail, and read Usenet newsgroup postings. Web/CGI Programming -- Yes, pure CGI is "sooo yesterday," but before you jump on all the web framework bandwagons, it's a good idea to learn basics and the basis of how all web servers deliver dynamic content back to the client browser so that you can appreciate all the work that is done on your behalf by a more fully-featured frame- work. Time-permitting, we will also give a high-level overview of one of the more popular Python web frameworks, Django. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - WHERE: near the San Francisco Airport (SFO/San Bruno), CA, USA WEB: http://cyberwebconsulting.com (click "Python Training") LOCALS: easy freeway (101/280/380) with lots of parking plus public transit (BART and CalTrain) access via the San Bruno stations, easily accessible from all parts of the Bay Area VISITORS: free shuttle to/from the airport, free high-speed internet, free breakfast and regular evening receptions; fully-equipped suites See website for costs, venue info, and registration. Discounts are available for multiple registrations as well as for teachers/students. Hope to see you there! -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com

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