🌐 Mailman 3 June 2009 - Python-list - python.org

Re: *Advanced* Python book?
by Michele Simionato March 25, 2010

March 25, 2010

On Jan 16, 9:27 pm, mk <mrk...(a)gmail.com> wrote: > Hello everyone, > > I looked for it I swear, but just can't find it. > > Most Python books seem to focus on examples of how to call functions > from standard library. I don't need that, I have online Python > documentation for that. > > I mean really advanced mental gymnastics, like gory details of how > Python objects operate, how to exploit its dynamic capabilities, dos and > donts with particular Python objects, advanced tricks, everything from > chained decorators to metaprogramming. Dive Into Python comes closest to > this ideal from what I have found, but still not far enough. > > Anybody found such holy grail? > > Regards, > mk "Expert Python Programming" by Tarek Ziadé is quite good and I wrote a review for it: http://www.artima.com/weblogs/viewpost.jsp?thread=240415 There is plenty of info about Advanced Python on the net, much more than in book form. Come to think of it, there are my Oxford lectures (the title was exactly "Advanced Python Programming") and I could republish it on my blog, since I cannot find them on the net anymore. Michele Simionato

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Turtle graphics speed(). Seems broken
by Alexander.Oot＠gmail.com Feb. 28, 2010

Feb. 28, 2010

I think the speed function may be broken from the turtle graphics package "from turtle import * speed('fastest') forward(50)" I have tried all of the different speed settings, but I get no change in the turtle's speed.... does anyone know how to fix this?

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llvm vs. parrot
by Paul Watson Sept. 28, 2009

Sept. 28, 2009

Is Parrot out of favor these days? It appears that Google is going to use llvm. http://code.google.com/p/unladen-swallow/

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Inheriting dictionary attributes and manipulate them in subclasses
by Dominik Ruf Sept. 12, 2009

Sept. 12, 2009

Hi, I just stumbled upon the following behaviour. >>> class base(): ... dic = {'1':'1', '2':'2'} ... >>> class child1(base): ... def __init__(self): ... self.dic.update({'1':'2'}) ... >>> class child2(base): ... pass ... >>> c1 = child1() >>> c2 = child2() >>> >>> print c1.dic {'1': '2', '2': '2'} >>> print c2.dic {'1': '2', '2': '2'} This is not what I have excepted. Although I know the solution to get what I want... >>> class base(): ... def __init__(self): ... self.dic = {'1':'1', '2':'2'} ... >>> class child1(base): ... def __init__(self): ... base.__init__(self) ... self.dic.update({'1':'2'}) ... >>> class child2(base): ... pass ... >>> c1 = child1() >>> c2 = child2() >>> >>> print c1.dic {'1': '2', '2': '2'} >>> print c2.dic {'1': '1', '2': '2'} ... I wonder if there is a special reason for the behaviour in the first example. Shouldn't the first example behave like the second? cheers Dominik

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Read a content file from a P7M
by Luca Aug. 28, 2009

Aug. 28, 2009

Hi all. There is standard or sugested way in python to read the content of a P7M file? I don't need no feature like verify sign, or sign using a certificate. I only need to extract the content file of the p7m (a doc, a pdf, ...) Thanks! -- -- luca

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Bash-like brace expansion
by Peter Waller Aug. 24, 2009

Aug. 24, 2009

Okay, I got fed up with there not being any (obvious) good examples of how to do bash-like brace expansion in Python, so I wrote it myself. Here it is for all to enjoy! If anyone has any better solutions or any other examples of how to do this, I'd be glad to hear from them. #~ BraceExpand.py - Bash-like brace expansion in Python #~ Copyright (C) 2009 <peter.waller(a)gmail.com> #~ This program is free software: you can redistribute it and/or modify #~ it under the terms of the GNU Affero General Public License as #~ published by the Free Software Foundation, either version 3 of the #~ License, or (at your option) any later version. #~ This program is distributed in the hope that it will be useful, #~ but WITHOUT ANY WARRANTY; without even the implied warranty of #~ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #~ GNU Affero General Public License for more details. #~ You should have received a copy of the GNU Affero General Public License #~ along with this program. If not, see <http://www.gnu.org/licenses/ >. import re from itertools import imap class NoBraces(Exception): pass def BraceExpand(text, ordering = []): """Recursively brace expand text in a bash-like fashion. See 'man 2 bash' under the heading 'Brace Expansion' Example: "/data/file{1..10}.root" expands to file1.root ... file9.root Ordering allows changing the order of iteration. The rules for this are a little complicated. Ordering is a list of boolean values. If it is possible to expand the postamble, the first value from the list is removed, and used to determine whether the postamble should be iterated over before iterating over the amble. The list is then passed down recursively to the next Brace. What does this code do? It is simpler than it looks. There are three main steps: 1) Split the string into three parts, consisting of pre-amble, amble and post-amble. (This requires keeping track of nested {}'s.) 2) In the amble, figure out which commas are not stuck in {}'s, and split the string by those commas. 3) For each part of this split string, Add together the pre- amble, the string and the post-amble. Call BraceExpand() on this string to deal with nested braces and any expansion required in the postamble Other things this code does which make it look more complicated: * Expand ranges along the lines of {1..10} * Allow for re-arranging the order of iteration Todo/Not Implemented: * Escaping/quoting Example C implementation from bash (inspiration for this): http://www.oldlinux.org/Linux.old/bin/old/bash-1.11/braces.c """ def FindMatchedBraces(text, position = -1): "Search for nested start and end brace in text starting from position" braceDepth = 0 nextClose = -1 first = True # Search for a { # is it closer than the nearest } ? # Yes : increase brace depth # No : decrease brace depth # When we reach braceDepth == 0, we have found our close brace while braceDepth or first: nextOpen = text.find("{", position+1) nextClose = text.find("}", position+1) if first and nextOpen >= 0: startBrace = nextOpen first = False if nextOpen < nextClose and nextOpen >= 0: braceDepth += 1 position = nextOpen elif nextClose >= 0: braceDepth -= 1 position = nextClose else: raise NoBraces() return startBrace, position try: start, end = FindMatchedBraces(text) except NoBraces: # There are no braces! Nothing to expand! return [text] # Split the text into three bits, '{pre,,post}amble'. The 'pre' is anything # before expansion, the '' is the bit that needs expanding and gluing to # the pre and the post. After gluing together, we can recursively expand # again preamble = text[:start] amble = text[start+1:end] postamble = text[end+1:] def BareCommaSearcher(amble): "Search for commas which are not encapsulated in {}" haveBraces = True try: start, end = FindMatchedBraces(amble) except NoBraces: haveBraces = False position = -1 while True: position = amble.find(",", position+1) if position < 0: # We didn't find any comma after 'position', finish searching. break if haveBraces and start < position < end: # We're inside some braces, skip to the end of them, find the # next set. position = end haveBraces = True try: start, end = FindMatchedBraces(amble, position) except NoBraces: haveBraces = False continue yield position # Reached the end of the string. (Conveniently "text"[pos:None] is the # same as "text"[pos:] yield None parts = [] rangeMatcher = re.compile(r"^(\d+)..(\d+)$") # Find each segment of the amble, splitting by 'bare' commas position = 0 for commaPos in BareCommaSearcher(amble): # Get a bit between bare commas part = amble[position:commaPos] # Found a matched range, expand it! matchedRange = rangeMatcher.match(part) if matchedRange: matchedIndices = map(int, matchedRange.groups()) parts.extend(imap(str,xrange(*matchedIndices))) else: parts.append(part) if not commaPos: # Avoid None + 1 at the end of iteration break position = commaPos + 1 # Is the postamble expandable? (Does it contain braces?) postambleExpandable = True try: start, end = FindMatchedBraces(postamble) except NoBraces: postambleExpandable = False # Check to see if we should iterate over postamble first, also sort out # iteration ordering postambleFirst = ordering thisPostambleFirst = False if postambleExpandable and postambleFirst: postambleFirst = list(postambleFirst) thisPostambleFirst = postambleFirst.pop(0) result = [] if postambleExpandable and thisPostambleFirst: # Iterate of expanded postamble first for postpart in BraceExpand(postamble): for part in parts: part = "".join([preamble, part, postpart]) result.extend(BraceExpand(part, postambleFirst)) else: for part in parts: part = "".join([preamble, part, postamble]) result.extend(BraceExpand(part, postambleFirst)) return result if __name__ == "__main__": from pprint import pprint pprint(BraceExpand("electron_{n,{pt,eta,phi}[{1,2}]}", ordering = [True])) #~ pprint(BraceExpand("Myfile{1,3..10}.root")) #~ pprint(BraceExpand("{pre,,post}amble")) #~ pprint(BraceExpand("amble{a,b,}}"))

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zlib interface semi-broken
by Travis Aug. 21, 2009

Aug. 21, 2009

Hello all, The zlib interface does not indicate when you've hit the end of a compressed stream. The underlying zlib functionality provides for this. With python's zlib, you have to read past the compressed data and into the uncompressed, which gets stored in Decompress.unused_data. As a result, if you've got a network protocol which mixes compressed and non-compressed output, you may find a compressed block ending with no uncompressed data following until you send another command -- which a synchronous (non-pipelined) client will not send, because it is waiting for the [compressed] data from the previous command to be finished. As a result, you get a protocol deadlock. A simple way to fix this would be to add a finished attribute to the Decompress object. However, perhaps this would be a good time to discuss how this library works; it is somewhat awkward and perhaps there are other changes which would make it cleaner. What does the python community think? -- Crypto ergo sum. http://www.subspacefield.org/~travis/ Do unto other faiths as you would have them do unto yours. If you are a spammer, please email john(a)subspacefield.org to get blacklisted.

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socket.inet_ntop, and pton question
by Andrew Aug. 5, 2009

Aug. 5, 2009

Hi Are these functions (inet_ntop(), inet_pton()) from the socket library supported on Windows. If not is there an equivalent for them using Windows Ive seen mention of people creating their own in order to use them Appreciate the help ty

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Unable to get Tkinter menubar to appear under OS X
by Eric Winter July 17, 2009

July 17, 2009

Hi all. I've googled this issue several times and come up dry. Here's the situation: I have a X-windows build of Tkinter for Python built on an OS X machine (10.4 or 10.5, same issue). This is not the Aqua version of Tk, but Tk built from source using X-Window support. I also use a from- source build of Python, not the system Python. I don't like this arrangement, but project requirements (allegedly) dictate this approach. When I run any application using that copy of Tkinter and that copy of Python, everything seems to work fine except menus - the code which creates the menus runs, but no menus appear, either in the window or at the top of the screen. Am I required to use the Aqua version of Tk on OS X? If not, do I need to do something special on OS X when I built Tk and/or Python? Any hints here would be greatly appreciated. Thanks, Eric Winter Fermi Science Support Center NASA Goddard Space Flight Center

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Proposal: Decimal literals in Python.
by Lennart Benschop July 14, 2009

July 14, 2009

Python has had the Decimal data type for some time now. The Decimal data type is ideal for financial calculations. Using this data type would be more intuitive to computer novices than float as its rounding behaviour matches more closely what humans expect. More to the point: 0.1 and 0.01 are exact in Decimal and not exact in float. Unfortunately it is not very easy to access the Decimal data type. To obtain the decimal number 12.34 one has to do something like this: import decimal x=decimal.Decimal("12.34") Of course we can intruduce a single character function name as an alias for the Decimal type constructor, but even then we have to use both parentheses and quotes for each and every decimal constant. We cannot make it shorter than D("12.34") With Python 3000 major changes to the language are carried out anyway. My proposal would require relatively minor changes. My proposal: - Any decimal constant suffixed with the letter "D" or "d" will be interpreted as a literal of the Decimal type. This also goes for decimal constants with exponential notation. Examples of decimal literals: 1d 12.34d 1e-3d (equivalent to 0.001d) 1e3d (same value as 1000d, but without trailing zeros). 1.25e5d (same value as 125000d but without trailing zeros). When we print a decimal number or convert it to a string with str(), a trailing d should not be added. The repr function does yield strings with a trailing d. When decimal numbers are converted from strings, both numbers with and without a trailing d should be accepted. If we have decimal literals in the core language, we should probably have a type constructor in the core namespace, e.g. dec() along with int() and float(). We then need the decimal module only for the more advanced stuff like setcontext. Pros: - the Decimal data type will be more readily accessible, especially for novices. - Traling characters at the end of a literal are already used (the L for long). - It does not conflict with the syntax of other numeric constants or language constructs. - It does not change the meaning of existing valid literal constants. Constants that used to be float will continue to do so. Cons: - The lexical scanner of the Python interpreter will be slightly more complex. - The d suffix for constants with exponential notation is ugly. - Decimal numbers with exponentail notation like 2e5d could be mistaken for hex (by humans, not by the parser as hex requires the 0x prefix). - It requires the decimal module to be part of the core Python interpreter. -- Lennart

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