🌐 Mailman 3 February 2005 - Python-list - python.org

ZoDB's capabilities
by Almad March 3, 2005

March 3, 2005

Hello, I'm going to write a custom CMS. I'd like to use some odbms, as code is then much more cleaner...however, i'm a little bit scared about capabilities of ZoDB, when compared with f. e. Firebird. How much instances is Zodb able to handle? Under "handle" I mean "in real time", not "theoretically". I'd like to use it for dynamic portal with about 2000 - 3000 UIP / day. And, how is it with stability and crash recovery? I can't find some more sources about zodb, when there are some other sources then those on Zope, please tell me. Or, please tell me if you knew some better odbms engine ^_^ Thanks, -- Lukas "Almad" Linhart [:: http://www.almad.net/ ::] [:: Humans are too complicated to be described with words. ::] [:: PGP/GNUPg key: http://www.almad.net/download/pubkey.asc ::]

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Python Online Programming Contest
by Varun March 2, 2005

March 2, 2005

Hi Friends, Department of Information Technology, Madras Institute of Technology, Anna University, India is conducting a technical symposium, Samhita. As a part of samhita, an Online Programming Contest is scheduled on Sunday, 27 Feb 2005. This is the first Online Programming Contest in India to support Python !!!!. Other languages supported are C and C++. For Registration and Rules of the contest, http://www.samhita.info/opc For details about samhita http://www.samhita.info/ Regards, -Online Programming Contest team

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HELP: Python equivalent of UNIX command "touch"
by pekka niiranen March 2, 2005

March 2, 2005

Does anybody know Python recipe for changing the date of the directory or files in W2K to current date and time? In UNIX shell command "touch" does it. -pekka-

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yield_all needed in Python
by Douglas Alan March 2, 2005

March 2, 2005

While writing a generator, I was just thinking how Python needs a "yield_all" statement. With the help of Google, I found a pre-existing discussion on this from a while back in the Lightweight Languages mailing list. I'll repost it here in order to improve the chances of this enhancement actually happening someday. The original poster from the LL mailing list seems mostly concerned with algorithmic efficiency, while I'm concerned more about making my programs shorter and easier to read. The ensuing discussion on the LL list talks about how yield_all would be somewhat difficult to implement if you want to get the efficiency gain desired, but I don't think it would be very difficult to implement if that goal weren't required, and the goal were limited to just the expressive elegance: A Problem with Python's 'yield' * To: LL1 Mailing List <address@hidden> * Subject: A Problem with Python's 'yield' * From: Eric Kidd <address@hidden> * Date: 27 May 2003 11:15:20 -0400 * Organization: * Sender: address@hidden I'm going to pick on Python here, but only because the example code will be short and sweet. :-) I believe several other implementations of generators have the same problem. Python's generator system, used naively, turns an O(N) tree traversal into an O(N log N) tree traversal: class Tree: def __init__(self, value, left=None, right=None): self.value = value self.left = left self.right = right def in_order(self): if self.left is not None: for v in self.left.in_order(): yield v yield self.value if self.right is not None: for v in self.right.in_order(): yield v t=Tree(2, Tree(1), Tree(3)) for v in yield_bug.t.in_order(): print v This prints: 1 2 3 Unfortunately, this snippet calls 'yield' 5 times, because the leaf values must be yielded twice on their way back up the tree. We can shorten the code--and make it run in O(N) time--by adding a new keyword to replace the "for v in ...: yield v" pattern: def in_order(self): if self.left is not None: yield_all self.left.in_order(): yield self.value if self.right is not None: yield_all self.right.in_order(): Interestingly enough, this allows you define notions such as "tail-recursive generation", and apply the usual bag of recursion-optimization techniques. Cheers, Eric |>oug

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[perl-python] generate all possible pairings
by Xah Lee March 2, 2005

March 2, 2005

20050226 exercise: generate all possible pairings given a list that is a set partitioned into subsets, generate a list of all possible pairings of elements in any two subset. Example: genpair( [[9,1],[5],[2,8,7]] ); returns: [[5,8],[9,5],[1,5],[9,2],[9,7],[1,8],[1,7],[5,2],[1,2],[9,8],[5,7]] (we do not assume the given set has order, so the result is not ordered.) Perl code and Python code will be posted in 2 days. This is brought to you by the perl-python community. To subscribe, see http://xahlee.org/perl-python/python.html Xah xah(a)xahlee.org http://xahlee.org/PageTwo_dir/more.html

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Re: Canonical way of dealing with null-separated lines?
by Douglas Alan March 2, 2005

March 2, 2005

Okay, here's the definitive version (or so say I). Some good doobie please make sure it makes its way into the standard library: def fileLineIter(inputFile, newline='\n', leaveNewline=False, readSize=8192): """Like the normal file iter but you can set what string indicates newline. You can also set the read size and control whether or not the newline string is left on the end of the iterated lines. Setting newline to '\0' is particularly good for use with an input file created with something like "os.popen('find -print0')". """ partialLine = [] while True: charsJustRead = inputFile.read(readSize) if not charsJustRead: break lines = charsJustRead.split(newline) if len(lines) > 1: partialLine.append(lines[0]) lines[0] = "".join(partialLine) partialLine = [lines.pop()] else: partialLine.append(lines.pop()) for line in lines: yield line + ("", newline)[leaveNewline] if partialLine and partialLine[-1] != '': yield "".join(partialLine) |>oug

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wxPython/IEHtmlWindow documentation (what events are available ?)
by richardshea＠despammed.com March 1, 2005

March 1, 2005

Hi - I've got a script which is making use of ... import wx.lib.iewin as iewin ... and so ... self.ie = iewin.IEHtmlWindow(self, -1, style = wx.NO_FULL_REPAINT_ON_RESIZE) ... but I can't find any documentation about what a IEHtmlWindow object might do - in particular what I might do with the events. I have some sample code and I've taken a look at iewin.py but what I would like to know is when the various events are going to fire ? 'DOCUMENTCOMPLETE' seems fairly self-explanatory but others such as 'BEFORENAVIGATE2' and 'STATUSTEXTCHANGE' are less guessable. I've looked at (what I think is) the MS documentation but I cannot find references to any of these events - can anyone point me information please ? Thanks Richard.

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Why do descriptors (and thus properties) only work on attributes.
by Antoon Pardon March 1, 2005

March 1, 2005

Can anyone explain why descriptors only work when they are an attribute to an object or class. I think a lot of interesting things one can do with descriptors would be just as interesting if the object stood on itself instead of being an attribute to an other object. So what are the reasons for limiting this feature in such a way? -- Antoon Pardon

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accessor/mutator functions
by mirandacascade＠yahoo.com March 1, 2005

March 1, 2005

When I look at how classes are set up in other languages (e.g. C++), I often observe the following patterns: 1) for each data member, the class will have an accessor member function (a Get<whatever> function) 2) for each data member, the class will have a mutator member function (a Set<whatver> function) 3) data members are never referenced directly; they are always referenced with the accessor and mutator functions My questions are: a) Are the three things above considered pythonic? b) What are the tradeoffs of using getattr() and setattr() rather than creating accessor and mutator functions for each data member?

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Re: accessor/mutator functions
by Nick Craig-Wood March 1, 2005

March 1, 2005

Michael Spencer <mahs(a)telcopartners.com> wrote: > mirandacascade(a)yahoo.com wrote: > > When I look at how classes are set up in other languages (e.g. C++), I > > often observe the following patterns: > > 1) for each data member, the class will have an accessor member > > function (a Get<whatever> function) > > 2) for each data member, the class will have a mutator member function > > (a Set<whatver> function) > > 3) data members are never referenced directly; they are always > > referenced with the accessor and mutator functions > > > > My questions are: > > a) Are the three things above considered pythonic? > > No > > > b) What are the tradeoffs of using getattr() and setattr() rather than > > creating accessor and mutator functions for each data member? > > Use property descriptors instead: > http://www.python.org/2.2.1/descrintro.html#property > http://users.rcn.com/python/download/Descriptor.htm#properties Actually I would say just access the attribute directly for both get and set, until it needs to do something special in which case use property(). The reason why people fill their code up with boiler plate get/set methods is to give them the flexibility to change the implementation without having to change any of the users. In python you just swap from direct attribute access to using property(). Also note that with property() you can make an attribute read only (by defining only the get method) which is often the encapsulation you really want - and that is something you can't do in C++. -- Nick Craig-Wood <nick(a)craig-wood.com> -- http://www.craig-wood.com/nick

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