Python-announce-list June 2001

python-announce-list@python.org

21 participants
33 discussions

[ANN] VideoCapture 0.2 released
by Markus Gritsch 24 Jun '01

24 Jun '01

VideoCapture-0.2 ================ URL: ---- http://stud4.tuwien.ac.at/~e9326522/VideoCapture/ What it is: ----------- VideoCapture is a Python extension for Win32 which makes it possible to access video-capture devices (e.g. a USB webcam). What is new in version 0.2: --------------------------- *) Added extensive error checking after every system call. In case something goes wrong an exception is raised. *) Some enhancements to the high level interface like selectable fontstyle, various shadow modes for better font legibility. *) The video-device that should be used can be specified. Contact: -------- Markus Gritsch (gritsch(a)iue.tuwien.ac.at) Enjoy and have fun!

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ANNOUNCE: web2ldap 0.9.4
by Michael Ströder 24 Jun '01

24 Jun '01

HI! Find a new release of web2ldap on: http://www.web2ldap.de/download.html web2ldap is a web-based generic LDAP client written in Python. Ciao, Michael. web2ldap 0.9.4 Release Date: 2001-06-23 Changes since 0.9.3: * Fixed displaying of iPAddress attribute in certificates. * Abandoned global configuration parameter web2ldapcnf.misc.script_method. * Slightly improved excpetion handling especially of logging/ignoring user-aborted connections, etc. * Determining appropriate charset used with browser was improved: mainly proper parsing of capability values. * A lookup of SRV RRs is automatically done if a LDAP URL does not contain a host name but a "dc-style" DN (a DN formed by domainComponent attributes). * New configuration sub-module fastcgi. * Some really significant performance optimizations in ldapthreading module. Former approach in method LDAPObject.result() was brain-dead and slow. * Web session ID is now passed around in PATH_INFO instead as a hidden form field. This means less HTML bloat and it decoupled session retrieving from form processing. * If ldap.NAMING_VIOLATION occurs during add the user can reedit his input. * Fixed smart login search with user names containing NON-ASCII chars. (sigh!) * Fixed wrong passing of parameters when calling function ldapbase.SmartLogin(). * Use timeout search for smart login.

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PEP 255: Simple Generators, Revised Posting
by Tim Peters 23 Jun '01

23 Jun '01

Major revision: more details about exceptions, return vs StopIteration, and interactions with try/except/finally; more Q&A; and a BDFL Pronouncement. The reference implementation appears solid and works as described here in all respects, so I expect this will be the last major revision (and so also last full posting) of this PEP. The output below is in ndiff format (see Tools/scripts/ndiff.py in your Python distribution). Just the new text can be seen in HTML form here: http://python.sf.net/peps/pep-0255.html "Feature discussions" should take place primarily on the Python Iterators list: mailto:python-iterators@lists.sourceforge.net Implementation discussions may wander in and out of Python-Dev too. PEP: 255 Title: Simple Generators - Version: $Revision: 1.3 $ ? ^ + Version: $Revision: 1.12 $ ? ^^ Author: nas(a)python.ca (Neil Schemenauer), tim.one(a)home.com (Tim Peters), magnus(a)hetland.org (Magnus Lie Hetland) Discussion-To: python-iterators(a)lists.sourceforge.net Status: Draft Type: Standards Track Requires: 234 Created: 18-May-2001 Python-Version: 2.2 - Post-History: 14-Jun-2001 + Post-History: 14-Jun-2001, 23-Jun-2001 ? +++++++++++++ Abstract This PEP introduces the concept of generators to Python, as well as a new statement used in conjunction with them, the "yield" statement. Motivation When a producer function has a hard enough job that it requires maintaining state between values produced, most programming languages offer no pleasant and efficient solution beyond adding a callback function to the producer's argument list, to be called with each value produced. For example, tokenize.py in the standard library takes this approach: the caller must pass a "tokeneater" function to tokenize(), called whenever tokenize() finds the next token. This allows tokenize to be coded in a natural way, but programs calling tokenize are typically convoluted by the need to remember between callbacks which token(s) were seen last. The tokeneater function in tabnanny.py is a good example of that, maintaining a state machine in global variables, to remember across callbacks what it has already seen and what it hopes to see next. This was difficult to get working correctly, and is still difficult for people to understand. Unfortunately, that's typical of this approach. An alternative would have been for tokenize to produce an entire parse of the Python program at once, in a large list. Then tokenize clients could be written in a natural way, using local variables and local control flow (such as loops and nested if statements) to keep track of their state. But this isn't practical: programs can be very large, so no a priori bound can be placed on the memory needed to materialize the whole parse; and some tokenize clients only want to see whether something specific appears early in the program (e.g., a future statement, or, as is done in IDLE, just the first indented statement), and then parsing the whole program first is a severe waste of time. Another alternative would be to make tokenize an iterator[1], delivering the next token whenever its .next() method is invoked. This is pleasant for the caller in the same way a large list of results would be, but without the memory and "what if I want to get out early?" drawbacks. However, this shifts the burden on tokenize to remember *its* state between .next() invocations, and the reader need only glance at tokenize.tokenize_loop() to realize what a horrid chore that would be. Or picture a recursive algorithm for producing the nodes of a general tree structure: to cast that into an iterator framework requires removing the recursion manually and maintaining the state of the traversal by hand. A fourth option is to run the producer and consumer in separate threads. This allows both to maintain their states in natural ways, and so is pleasant for both. Indeed, Demo/threads/Generator.py in the Python source distribution provides a usable synchronized-communication class for doing that in a general way. This doesn't work on platforms without threads, though, and is very slow on platforms that do (compared to what is achievable without threads). A final option is to use the Stackless[2][3] variant implementation of Python instead, which supports lightweight coroutines. This has much the same programmatic benefits as the thread option, but is much more efficient. However, Stackless is a controversial rethinking of the Python core, and it may not be possible for Jython to implement the same semantics. This PEP isn't the place to debate that, so suffice it to say here that generators provide a useful subset of Stackless functionality in a way that fits easily into the current CPython implementation, and is believed to be relatively straightforward for other Python implementations. That exhausts the current alternatives. Some other high-level languages provide pleasant solutions, notably iterators in Sather[4], which were inspired by iterators in CLU; and generators in Icon[5], a novel language where every expression "is a generator". There are differences among these, but the basic idea is the same: provide a kind of function that can return an intermediate result ("the next value") to its caller, but maintaining the function's local state so that the function can be resumed again right where it left off. A very simple example: def fib(): a, b = 0, 1 while 1: yield b a, b = b, a+b When fib() is first invoked, it sets a to 0 and b to 1, then yields b back to its caller. The caller sees 1. When fib is resumed, from its point of view the yield statement is really the same as, say, a print statement: fib continues after the yield with all local state intact. a and b then become 1 and 1, and fib loops back to the yield, yielding 1 to its invoker. And so on. From fib's point of view it's just delivering a sequence of results, as if via callback. But from its caller's point of view, the fib invocation is an iterable object that can be resumed at will. As in the thread approach, this allows both sides to be coded in the most natural ways; but unlike the thread approach, this can be done efficiently and on all platforms. Indeed, resuming a generator should be no more expensive than a function call. The same kind of approach applies to many producer/consumer functions. For example, tokenize.py could yield the next token instead of invoking a callback function with it as argument, and tokenize clients could iterate over the tokens in a natural way: a Python generator is a kind of Python iterator[1], but of an especially powerful kind. - Specification + Specification: Yield ? ++++++++ A new statement is introduced: yield_stmt: "yield" expression_list "yield" is a new keyword, so a future statement[8] is needed to phase - this in. [XXX spell this out] + this in. [XXX spell this out -- but new keywords have ripple effects + across tools too, and it's not clear this can be forced into the future + framework at all -- it's not even clear that Python's parser alone can + be taught to swing both ways based on a future stmt] The yield statement may only be used inside functions. A function that - contains a yield statement is called a generator function. + contains a yield statement is called a generator function. A generator ? +++++++++++++ + function is an ordinary function object in all respects, but has the + new CO_GENERATOR flag set in the code object's co_flags member. When a generator function is called, the actual arguments are bound to function-local formal argument names in the usual way, but no code in the body of the function is executed. Instead a generator-iterator object is returned; this conforms to the iterator protocol[6], so in particular can be used in for-loops in a natural way. Note that when the intent is clear from context, the unqualified name "generator" may be used to refer either to a generator-function or a generator- iterator. Each time the .next() method of a generator-iterator is invoked, the code in the body of the generator-function is executed until a yield or return statement (see below) is encountered, or until the end of the body is reached. If a yield statement is encountered, the state of the function is frozen, and the value of expression_list is returned to .next()'s caller. By "frozen" we mean that all local state is retained, including the current bindings of local variables, the instruction pointer, and the internal evaluation stack: enough information is saved so that the next time .next() is invoked, the function can proceed exactly as if the yield statement were just another external call. + Restriction: A yield statement is not allowed in the try clause of a + try/finally construct. The difficulty is that there's no guarantee + the generator will ever be resumed, hence no guarantee that the finally + block will ever get executed; that's too much a violation of finally's + purpose to bear. + + + Specification: Return + A generator function can also contain return statements of the form: "return" Note that an expression_list is not allowed on return statements in the body of a generator (although, of course, they may appear in the bodies of non-generator functions nested within the generator). - When a return statement is encountered, nothing is returned, but a + When a return statement is encountered, control proceeds as in any + function return, executing the appropriate finally clauses (if any - StopIteration exception is raised, signalling that the iterator is ? ------------ + exist). Then a StopIteration exception is raised, signalling that the ? ++++++++++++++++ - exhausted. The same is true if control flows off the end of the + iterator is exhausted. A StopIteration exception is also raised if + control flows off the end of the generator without an explict return. + - function. Note that return means "I'm done, and have nothing ? ----------- + Note that return means "I'm done, and have nothing interesting to ? +++++++++++++++ - interesting to return", for both generator functions and non-generator ? --------------- + return", for both generator functions and non-generator functions. ? +++++++++++ - functions. + + Note that return isn't always equivalent to raising StopIteration: the + difference lies in how enclosing try/except constructs are treated. + For example, + + >>> def f1(): + ... try: + ... return + ... except: + ... yield 1 + >>> print list(f1()) + [] + + because, as in any function, return simply exits, but + + >>> def f2(): + ... try: + ... raise StopIteration + ... except: + ... yield 42 + >>> print list(f2()) + [42] + + because StopIteration is captured by a bare "except", as is any + exception. + + + Specification: Generators and Exception Propagation + + If an unhandled exception-- including, but not limited to, + StopIteration --is raised by, or passes through, a generator function, + then the exception is passed on to the caller in the usual way, and + subsequent attempts to resume the generator function raise + StopIteration. In other words, an unhandled exception terminates a + generator's useful life. + + Example (not idiomatic but to illustrate the point): + + >>> def f(): + ... return 1/0 + >>> def g(): + ... yield f() # the zero division exception propagates + ... yield 42 # and we'll never get here + >>> k = g() + >>> k.next() + Traceback (most recent call last): + File "<stdin>", line 1, in ? + File "<stdin>", line 2, in g + File "<stdin>", line 2, in f + ZeroDivisionError: integer division or modulo by zero + >>> k.next() # and the generator cannot be resumed + Traceback (most recent call last): + File "<stdin>", line 1, in ? + StopIteration + >>> + + + Specification: Try/Except/Finally + + As noted earlier, yield is not allowed in the try clause of a try/ + finally construct. A consequence is that generators should allocate + critical resources with great care. There is no restriction on yield + otherwise appearing in finally clauses, except clauses, or in the try + clause of a try/except construct: + + >>> def f(): + ... try: + ... yield 1 + ... try: + ... yield 2 + ... 1/0 + ... yield 3 # never get here + ... except ZeroDivisionError: + ... yield 4 + ... yield 5 + ... raise + ... except: + ... yield 6 + ... yield 7 # the "raise" above stops this + ... except: + ... yield 8 + ... yield 9 + ... try: + ... x = 12 + ... finally: + ... yield 10 + ... yield 11 + >>> print list(f()) + [1, 2, 4, 5, 8, 9, 10, 11] + >>> Example # A binary tree class. class Tree: def __init__(self, label, left=None, right=None): self.label = label self.left = left self.right = right def __repr__(self, level=0, indent=" "): s = level*indent + `self.label` if self.left: s = s + "\n" + self.left.__repr__(level+1, indent) if self.right: s = s + "\n" + self.right.__repr__(level+1, indent) return s def __iter__(self): return inorder(self) # Create a Tree from a list. def tree(list): n = len(list) if n == 0: return [] i = n / 2 return Tree(list[i], tree(list[:i]), tree(list[i+1:])) # A recursive generator that generates Tree leaves in in-order. def inorder(t): if t: for x in inorder(t.left): yield x yield t.label for x in inorder(t.right): yield x # Show it off: create a tree. t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ") # Print the nodes of the tree in in-order. for x in t: print x, print # A non-recursive generator. def inorder(node): stack = [] while node: while node.left: stack.append(node) node = node.left yield node.label while not node.right: try: node = stack.pop() except IndexError: return yield node.label node = node.right # Exercise the non-recursive generator. for x in t: print x, print + Both output blocks display: + + A B C D E F G H I J K L M N O P Q R S T U V W X Y Z + Q & A + Q. Why not a new keyword instead of reusing "def"? + + A. See BDFL Pronouncements section below. + - Q. Why a new keyword? Why not a builtin function instead? + Q. Why a new keyword for "yield"? Why not a builtin function instead? ? ++++++++++++ A. Control flow is much better expressed via keyword in Python, and yield is a control construct. It's also believed that efficient implementation in Jython requires that the compiler be able to determine potential suspension points at compile-time, and a new - keyword makes that easy. + keyword makes that easy. The CPython referrence implementation also + exploits it heavily, to detect which functions *are* generator- + functions (although a new keyword in place of "def" would solve that + for CPython -- but people asking the "why a new keyword?" question + don't want any new keyword). + + Q: Then why not some other special syntax without a new keyword? For + example, one of these instead of "yield 3": + + return 3 and continue + return and continue 3 + return generating 3 + continue return 3 + return >> , 3 + from generator return 3 + return >> 3 + return << 3 + >> 3 + << 3 + + A: Did I miss one <wink>? Out of hundreds of messages, I counted two + suggesting such an alternative, and extracted the above from them. + It would be nice not to need a new keyword, but nicer to make yield + very clear -- I don't want to have to *deduce* that a yield is + occurring from making sense of a previously senseless sequence of + keywords or operators. Still, if this attracts enough interest, + proponents should settle on a single consensus suggestion, and Guido + will Pronounce on it. + + Q. Why allow "return" at all? Why not force termination to be spelled + "raise StopIteration"? + + A. The mechanics of StopIteration are low-level details, much like the + mechanics of IndexError in Python 2.1: the implementation needs to + do *something* well-defined under the covers, and Python exposes + these mechanisms for advanced users. That's not an argument for + forcing everyone to work at that level, though. "return" means "I'm + done" in any kind of function, and that's easy to explain and to use. + Note that "return" isn't always equivalent to "raise StopIteration" + in try/except construct, either (see the "Specification: Return" + section). + + Q. Then why not allow an expression on "return" too? + + A. Perhaps we will someday. In Icon, "return expr" means both "I'm + done", and "but I have one final useful value to return too, and + this is it". At the start, and in the absence of compelling uses + for "return expr", it's simply cleaner to use "yield" exclusively + for delivering values. + + + BDFL Pronouncements + + Issue: Introduce another new keyword (say, "gen" or "generator") in + place of "def", or otherwise alter the syntax, to distinguish + generator-functions from non-generator functions. + + Con: In practice (how you think about them), generators *are* + functions, but with the twist that they're resumable. The mechanics of + how they're set up is a comparatively minor technical issue, and + introducing a new keyword would unhelpfully overemphasize the + mechanics of how generators get started (a vital but tiny part of a + generator's life). + + Pro: In reality (how you think about them), generator-functions are + actually factory functions that produce generator-iterators as if by + magic. In this respect they're radically different from non-generator + functions, acting more like a constructor than a function, so reusing + "def" is at best confusing. A "yield" statement buried in the body is + not enough warning that the semantics are so different. + + BDFL: "def" it stays. No argument on either side is totally + convincing, so I have consulted my language designer's intuition. It + tells me that the syntax proposed in the PEP is exactly right - not too + hot, not too cold. But, like the Oracle at Delphi in Greek mythology, + it doesn't tell me why, so I don't have a rebuttal for the arguments + against the PEP syntax. The best I can come up with (apart from + agreeing with the rebuttals ... already made) is "FUD". If this had + been part of the language from day one, I very much doubt it would have + made Andrew Kuchling's "Python Warts" page. Reference Implementation - A preliminary patch against the CVS Python source is available[7]. + The current implementation, in a preliminary state (no docs and no + focused tests), is part of Python's CVS development tree[9]. + Using this requires that you build Python from source. + + This was derived from an earlier patch by Neil Schemenauer[7]. Footnotes and References [1] PEP 234, http://python.sf.net/peps/pep-0234.html [2] http://www.stackless.com/ [3] PEP 219, http://python.sf.net/peps/pep-0219.html [4] "Iteration Abstraction in Sather" Murer , Omohundro, Stoutamire and Szyperski http://www.icsi.berkeley.edu/~sather/Publications/toplas.html [5] http://www.cs.arizona.edu/icon/ [6] The concept of iterators is described in PEP 234 http://python.sf.net/peps/pep-0234.html [7] http://python.ca/nas/python/generator.diff [8] http://python.sf.net/peps/pep-0236.html + [9] To experiment with this implementation, check out Python from CVS + according to the instructions at + http://sf.net/cvs/?group_id=5470 Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil End:

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Python 2.0.1 released!
by Guido van Rossum 22 Jun '01

22 Jun '01

I'm happy to announce Python 2.0.1 -- the final release of the first Python version in a long time whose license is fully compatible with the GPL: http://www.python.org/2.0.1/ I thank Moshe Zadka who did almost all of the work to make this a useful bugfix release, and then went incommunicado for several weeks. (I hope you're OK, Moshe!) Compared to the release candidate, we've fixed a few typos in the license, tweaked the documentation a bit, and fixed an indentation error in statcache.py; other than that, the release candidate was perfect. :-) Python 2.0 users should be able to replace their 2.0 installation with the 2.0.1 release without any ill effects; apart from the license change, we've only fixed bugs that didn't require us to make feature changes. The SRE package (regular expression matching, used by the "re" module) was brought in line with the version distributed with Python 2.1; this is stable feature-wise but much improved bug-wise. For the full scoop, see the release notes on SourceForge: http://sourceforge.net/project/shownotes.php?release_id=40616 Python 2.1 users can ignore this release, unless they have an urgent need for a GPL-compatible Python version and are willing to downgrade. Rest assured that we're planning a bugfix release there too: I expect that Python 2.1.1 will be released within a month, with the same GPL-compatible license. (Right, Thomas?) We don't intend to build RPMs for 2.0.1. If someone else is interested in doing so, we can link to them. --Guido van Rossum (home page: http://www.python.org/~guido/)

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python-dev summary 2001-06-07 - 2001-06-21
by Michael Hudson 22 Jun '01

22 Jun '01

This is a summary of traffic on the python-dev mailing list between June 7 and June 21 (inclusive) 2001. It is intended to inform the wider Python community of ongoing developments. To comment, just post to python-list(a)python.org or comp.lang.python in the usual way. Give your posting a meaningful subject line, and if it's about a PEP, include the PEP number (e.g. Subject: PEP 201 - Lockstep iteration) All python-dev members are interested in seeing ideas discussed by the community, so don't hesitate to take a stance on a PEP if you have an opinion. This is the tenth summary written by Michael Hudson. Summaries are archived at: <http://starship.python.net/crew/mwh/summaries/> Posting distribution (with apologies to mbm) Number of articles in summary: 192 | [|] | [|] 30 | [|] | [|] | [|] | [|] | [|] | [|] [|] 20 | [|] [|] | [|] [|] [|] | [|] [|] [|] [|] | [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] 10 | [|] [|] [|] [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] [|] [|] [|] [|] | [|] [|] [|] [|] [|] [|] [|] [|] [|] [|] [|] [|] 0 +-019-014-001-003-014-039-026-013-009-004-001-005-023-021 Thu 07| Sat 09| Mon 11| Wed 13| Fri 15| Sun 17| Tue 19| Fri 08 Sun 10 Tue 12 Thu 14 Sat 16 Mon 18 Wed 20 Quiet fortnight. * Adding .decode() method to Unicode * Marc-Andre Lemburg asked for opinions on adding a .decode method to unicode objects: <http://mail.python.org/pipermail/python-dev/2001-June/015346.html> He certainly got them; the responses ranged from neutral to negative, and there was a surprising amount of hostility in the air. The problem (as ever in these matters) seems to be that Python currently uses the same type for 8-bit strings and gobs of arbitrary data. Guido came to the rescue and calmed everyone down: <http://mail.python.org/pipermail/python-dev/2001-June/015404.html> since when discussion has vanished again. * Adding Asian codecs to the core * Marc-Andre Lemburg announced that Tamito KAJIYAMA has decided to relicense his Japanese codecs with a BSD-style license, enabling them to be included in the core: <http://mail.python.org/pipermail/python-dev/2001-June/015347.html> This is clearly a good thing; the only quibble is that the encodings are by their nature rather large, so they will probably go into a separate directory in CVS (probably python/dist/encodings/) and not go into the source tarball released on python.org. * Omit printing newline after newline * As readers of comp.lang.python will have noticed, Guido posted: <http://mail.python.org/pipermail/python-dev/2001-June/015350.html> and retracted: <http://mail.python.org/pipermail/python-dev/2001-June/015411.html> PEP 259, a proposal for changing the behaviour of the print statement. * sre "improvements" * Gustavo Niemeyer asked if anyone planned to add the "(?(1)blah)" re operators to Python: <http://mail.python.org/pipermail/python-dev/2001-June/015408.html> but Python is not perl and there wasn't much support for making regular expressions more baffling than they already are. * Generators * In a discussion that slobbered across comp.lang.python, python-dev and the python-iterators list at sf (and belongs on the latter!) there was much talk of PEP 255, Simple Generators. Most was positive; the main dissent was from people that thought it was too hard to tell a generator from a regular function (at the source level). However Guido listened to Tim's repeated claims that this is insignificant once you've actually used generators once or twice and Pronounced "'def' it is": <http://mail.python.org/pipermail/python-dev/2001-June/015500.html> and noticed that there are still some issues wrt try/finally blocks. However, clever people seem to be thinking about it, so I'm sure the problem's days are numbered :-) I should also note that the gen-branch has been checked into the trunk of CVS. Woohoo! Cheers, M.

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[ANN] QuantLib-Python 0.1.9
by Ferdinando Ametrano 19 Jun '01

19 Jun '01

QuantLib-Python is the SWIG Python wrap of QuantLib. QuantLib (http://quantlib.org) is a C++ open source library for quantitative finance. Version 0.1.9 of the C++ library and the Python extension have been released two weeks ago. QuantLib license is XFree86-style. The QuantLib project is aimed to provide a comprehensive software framework for quantitative finance. The goal is to provide a standard free/open-source library to quantitative analysts and developers for modelling, trading, and risk management in real-life. The core library is written in C++ and currently exported as a Python module. Modules are planned for other scripting languages, Excel, MatLab, etc. QuantLib plans to offer tools that are useful for both practical implementation, with features such as market conventions, solvers, PDEs, etc., and advanced modelling, e.g., exotic options and interest rate models. QuantLib is for academics and practitioners. The project is in alpha status, not ready for end-users yet but the time is right for major contributions to the design and the code base. Please consider joining one of the available mailing lists: quantlib-announce http://lists.sourceforge.net/mailman/listinfo/quantlib-announce quantlib-users http://lists.sourceforge.net/mailman/listinfo/quantlib-users quantlib-cvs http://lists.sourceforge.net/mailman/listinfo/quantlib-cvs Ferdinando Ametrano (ferdinando(a)ametrano.net) <P><A HREF="http://quantlib.org">QuantLib-Python</A> - An open source library for quantitative finance. (19-Jun-01)</P>

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[Application] B.Y.P. Server v.2.4.1. beta
by B.Y.P.Server 2.4.1.Beta 19 Jun '01

19 Jun '01

B.Y.P. Server v.2.4.1. beta --------------------------- Server to manage this clients over internet! The site was rebuilt. The target of this project was extended to support some thin clients developed with a wide range of GUI and languages (Borland Delphi, Java, Visual Basic, ncurses, KDE, Gnome, etc...) URL: http://OpenSourceDirectory.org/projects/bypserver License: GPL Categories: Net Applications, Server B.Y.P. Server 2.4.1. Beta (manotti(a)bigfoot.com) http://OpenSourceDirectory.org/projects/bypserver -- <a href="http://OpenSourceDirectory.org/projects/bypserver">B.Y.P. Server v.2.4.1. beta</a> -- Server to manage this clients over internet!

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Sybase module 0.26 released
by Dave Cole 19 Jun '01

19 Jun '01

What is it: The Sybase module provides a Python interface to the Sybase relational database system. The Sybase package supports almost all of the Python Database API, version 2.0 with extensions. The module works with Python versions 1.5.2 and later and Sybase versions 11.0.3 and later. It is based on the Sybase Client Library (ct_* API), and the Bulk-Library Client (blk_* API) interfaces. The 0.20 and later releases are a reimplementation of the module using a thin C wrapper on the Sybase-CT API, and a Python module to provide the DB-API functionality. It is still a work in progress, but should be good enough for most purposes. Changes for this release: - A collection of Sybase example programs was found and converted to use the sybasect module. This highlighted some bugs and many omissions. For the curious the example programs have been included in the release. array_bind.py diag_example.py mult_text.py bulkcopy.py dynamic_cur.py params.py cursor_sel.py dynamic_ins.py rpc.py cursor_upd.py example.py timeout.py On the whole I have avoided relying on using Sybase CT library callback functions. The timeout.py example program requires the use of a callback. Since callbacks cause the Python interpreter to be reentered, you cannot compile the module with multi-thread support. This is controlled via the WANT_THREADS #define in sybasect.h - The ntsetup.py distutils program was merged into the setup.py - The Buffer type was renamed to DataBuf to avoid type name clashes with the Python BufferType. - Bug was fixed in blk_bind() which was passing Python type object by value instead of by reference - oops. - All of the extension types in the sybasect module are now exported. - More work has been done on the documentation. There is very little outstanding programming work for the module. Most future work will be concentrated on the documentation. Where can you get it: http://www.object-craft.com.au/projects/sybase/ - Dave -- http://www.object-craft.com.au

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ANN: Introducing PLY-1.0 (Python Lex-Yacc)
by David Beazley 19 Jun '01

19 Jun '01

June 18, 2001 Announcing : PLY-1.0 (Python Lex-Yacc) http://systems.cs.uchicago.edu/ply Just when you thought it was safe, I'm pleased to announce the availability of an entirely new Python parser construction tool. PLY is a 100% Python implementation of the common parsing tools lex and yacc. Although several other parsing tools are available for Python, there are several reasons why you might want to consider PLY: - The tools are very closely modeled after traditional lex/yacc. If you know how to use these tools in C, you will find PLY to be similar. - PLY provides *very* extensive error reporting and diagnostic information to assist in parser construction. The original implementation was developed for instructional purposes. As a result, the system tries to identify the most common types of errors made by novice users. - PLY provides full support for empty productions, error recovery, precedence rules, and moderately ambiguous grammars. - Parsing is based on LR-parsing which is fast, memory efficient, better suited to large grammars, and which has a number of nice properties when dealing with syntax errors and other parsing problems. Currently, PLY builds its parsing tables using the SLR algorithm which is slightly weaker than LALR(1) which is used in traditional yacc. - Like John Aycock's excellent SPARK toolkit, PLY uses Python reflection to build lexers and parsers. This greatly simplifies the task of parser construction since it reduces the number of files and eliminates the need to run a separate lex/yacc tool before running your program. - PLY can be used to build parsers for large programming languages. Although it is not ultra-fast due to its Python implementation, PLY can be used to parse grammars consisting of several hundred rules (as might be found for a language like C). The lexer and LR parser are also reasonably efficient when parsing normal sized programs. The original version of PLY was developed for an Introduction to Compilers course where students used it to build a compiler for a simple Pascal-like language. Their compiler had to include lexical analysis, parsing, type checking, type inference, nested scoping, and generation of assembly code for the SPARC processor. Because of this, the current implementation has been extensively tested and debugged. In addition, most of the API and error checking facilities have been adapted to address common usability problems. More information about PLY can be obtained on the PLY webpage at: http://systems.cs.uchicago.edu/ply PLY is freely available and is licensed under the terms of the Lesser GNU Public License (LGPL). Cheers, David Beazley (beazley(a)cs.uchicago.edu)

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ANN: VideoCapture-0.1 - video device access (e.g. USB webcams)
by Markus Gritsch 18 Jun '01

18 Jun '01

VideoCapture-0.1 ================ URL: ---- http://stud4.tuwien.ac.at/~e9326522/VideoCapture/ What it is: ----------- VideoCapture is a Python extension for Win32 which makes it possible to access the video device (e.g. a USB webcam). It consists of a low-level native module (vidcap.pyd) and a high-level module written in Python (VideoCapture.py) which should be used solely. Contact: -------- Markus Gritsch (gritsch(a)iue.tuwien.ac.at) Enjoy and have fun! <P><A HREF="http://stud4.tuwien.ac.at/~e9326522/VideoCapture/">VideoCapture-0.1</A > - A Win32 Python Extension for Accessing the Video Device (e.g. a USB WebCam). (18-Jun-2001)

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Python-announce-list June 2001