Mailman 3 July 2003 - Python-Dev

PEP 1, PEP Purpose and Guidelines
by barry＠zope.com May 18, 2021

May 18, 2021

It has been a while since I posted a copy of PEP 1 to the mailing lists and newsgroups. I've recently done some updating of a few sections, so in the interest of gaining wider community participation in the Python development process, I'm posting the latest revision of PEP 1 here. A version of the PEP is always available on-line at http://www.python.org/peps/pep-0001.html Enjoy, -Barry -------------------- snip snip -------------------- PEP: 1 Title: PEP Purpose and Guidelines Version: $Revision: 1.36 $ Last-Modified: $Date: 2002/07/29 18:34:59 $ Author: Barry A. Warsaw, Jeremy Hylton Status: Active Type: Informational Created: 13-Jun-2000 Post-History: 21-Mar-2001, 29-Jul-2002 What is a PEP? PEP stands for Python Enhancement Proposal. A PEP is a design document providing information to the Python community, or describing a new feature for Python. The PEP should provide a concise technical specification of the feature and a rationale for the feature. We intend PEPs to be the primary mechanisms for proposing new features, for collecting community input on an issue, and for documenting the design decisions that have gone into Python. The PEP author is responsible for building consensus within the community and documenting dissenting opinions. Because the PEPs are maintained as plain text files under CVS control, their revision history is the historical record of the feature proposal[1]. Kinds of PEPs There are two kinds of PEPs. A standards track PEP describes a new feature or implementation for Python. An informational PEP describes a Python design issue, or provides general guidelines or information to the Python community, but does not propose a new feature. Informational PEPs do not necessarily represent a Python community consensus or recommendation, so users and implementors are free to ignore informational PEPs or follow their advice. PEP Work Flow The PEP editor, Barry Warsaw <peps(a)python.org>, assigns numbers for each PEP and changes its status. The PEP process begins with a new idea for Python. It is highly recommended that a single PEP contain a single key proposal or new idea. The more focussed the PEP, the more successfully it tends to be. The PEP editor reserves the right to reject PEP proposals if they appear too unfocussed or too broad. If in doubt, split your PEP into several well-focussed ones. Each PEP must have a champion -- someone who writes the PEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The PEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is PEP-able. Small enhancements or patches often don't need a PEP and can be injected into the Python development work flow with a patch submission to the SourceForge patch manager[2] or feature request tracker[3]. The PEP champion then emails the PEP editor <peps(a)python.org> with a proposed title and a rough, but fleshed out, draft of the PEP. This draft must be written in PEP style as described below. If the PEP editor approves, he will assign the PEP a number, label it as standards track or informational, give it status 'draft', and create and check-in the initial draft of the PEP. The PEP editor will not unreasonably deny a PEP. Reasons for denying PEP status include duplication of effort, being technically unsound, not providing proper motivation or addressing backwards compatibility, or not in keeping with the Python philosophy. The BDFL (Benevolent Dictator for Life, Guido van Rossum) can be consulted during the approval phase, and is the final arbitrator of the draft's PEP-ability. If a pre-PEP is rejected, the author may elect to take the pre-PEP to the comp.lang.python newsgroup (a.k.a. python-list(a)python.org mailing list) to help flesh it out, gain feedback and consensus from the community at large, and improve the PEP for re-submission. The author of the PEP is then responsible for posting the PEP to the community forums, and marshaling community support for it. As updates are necessary, the PEP author can check in new versions if they have CVS commit permissions, or can email new PEP versions to the PEP editor for committing. Standards track PEPs consists of two parts, a design document and a reference implementation. The PEP should be reviewed and accepted before a reference implementation is begun, unless a reference implementation will aid people in studying the PEP. Standards Track PEPs must include an implementation - in the form of code, patch, or URL to same - before it can be considered Final. PEP authors are responsible for collecting community feedback on a PEP before submitting it for review. A PEP that has not been discussed on python-list(a)python.org and/or python-dev(a)python.org will not be accepted. However, wherever possible, long open-ended discussions on public mailing lists should be avoided. Strategies to keep the discussions efficient include, setting up a separate SIG mailing list for the topic, having the PEP author accept private comments in the early design phases, etc. PEP authors should use their discretion here. Once the authors have completed a PEP, they must inform the PEP editor that it is ready for review. PEPs are reviewed by the BDFL and his chosen consultants, who may accept or reject a PEP or send it back to the author(s) for revision. Once a PEP has been accepted, the reference implementation must be completed. When the reference implementation is complete and accepted by the BDFL, the status will be changed to `Final.' A PEP can also be assigned status `Deferred.' The PEP author or editor can assign the PEP this status when no progress is being made on the PEP. Once a PEP is deferred, the PEP editor can re-assign it to draft status. A PEP can also be `Rejected'. Perhaps after all is said and done it was not a good idea. It is still important to have a record of this fact. PEPs can also be replaced by a different PEP, rendering the original obsolete. This is intended for Informational PEPs, where version 2 of an API can replace version 1. PEP work flow is as follows: Draft -> Accepted -> Final -> Replaced ^ +----> Rejected v Deferred Some informational PEPs may also have a status of `Active' if they are never meant to be completed. E.g. PEP 1. What belongs in a successful PEP? Each PEP should have the following parts: 1. Preamble -- RFC822 style headers containing meta-data about the PEP, including the PEP number, a short descriptive title (limited to a maximum of 44 characters), the names, and optionally the contact info for each author, etc. 2. Abstract -- a short (~200 word) description of the technical issue being addressed. 3. Copyright/public domain -- Each PEP must either be explicitly labelled as placed in the public domain (see this PEP as an example) or licensed under the Open Publication License[4]. 4. Specification -- The technical specification should describe the syntax and semantics of any new language feature. The specification should be detailed enough to allow competing, interoperable implementations for any of the current Python platforms (CPython, JPython, Python .NET). 5. Motivation -- The motivation is critical for PEPs that want to change the Python language. It should clearly explain why the existing language specification is inadequate to address the problem that the PEP solves. PEP submissions without sufficient motivation may be rejected outright. 6. Rationale -- The rationale fleshes out the specification by describing what motivated the design and why particular design decisions were made. It should describe alternate designs that were considered and related work, e.g. how the feature is supported in other languages. The rationale should provide evidence of consensus within the community and discuss important objections or concerns raised during discussion. 7. Backwards Compatibility -- All PEPs that introduce backwards incompatibilities must include a section describing these incompatibilities and their severity. The PEP must explain how the author proposes to deal with these incompatibilities. PEP submissions without a sufficient backwards compatibility treatise may be rejected outright. 8. Reference Implementation -- The reference implementation must be completed before any PEP is given status 'Final,' but it need not be completed before the PEP is accepted. It is better to finish the specification and rationale first and reach consensus on it before writing code. The final implementation must include test code and documentation appropriate for either the Python language reference or the standard library reference. PEP Template PEPs are written in plain ASCII text, and should adhere to a rigid style. There is a Python script that parses this style and converts the plain text PEP to HTML for viewing on the web[5]. PEP 9 contains a boilerplate[7] template you can use to get started writing your PEP. Each PEP must begin with an RFC822 style header preamble. The headers must appear in the following order. Headers marked with `*' are optional and are described below. All other headers are required. PEP: <pep number> Title: <pep title> Version: <cvs version string> Last-Modified: <cvs date string> Author: <list of authors' real names and optionally, email addrs> * Discussions-To: <email address> Status: <Draft | Active | Accepted | Deferred | Final | Replaced> Type: <Informational | Standards Track> * Requires: <pep numbers> Created: <date created on, in dd-mmm-yyyy format> * Python-Version: <version number> Post-History: <dates of postings to python-list and python-dev> * Replaces: <pep number> * Replaced-By: <pep number> The Author: header lists the names and optionally, the email addresses of all the authors/owners of the PEP. The format of the author entry should be address(a)dom.ain (Random J. User) if the email address is included, and just Random J. User if the address is not given. If there are multiple authors, each should be on a separate line following RFC 822 continuation line conventions. Note that personal email addresses in PEPs will be obscured as a defense against spam harvesters. Standards track PEPs must have a Python-Version: header which indicates the version of Python that the feature will be released with. Informational PEPs do not need a Python-Version: header. While a PEP is in private discussions (usually during the initial Draft phase), a Discussions-To: header will indicate the mailing list or URL where the PEP is being discussed. No Discussions-To: header is necessary if the PEP is being discussed privately with the author, or on the python-list or python-dev email mailing lists. Note that email addresses in the Discussions-To: header will not be obscured. Created: records the date that the PEP was assigned a number, while Post-History: is used to record the dates of when new versions of the PEP are posted to python-list and/or python-dev. Both headers should be in dd-mmm-yyyy format, e.g. 14-Aug-2001. PEPs may have a Requires: header, indicating the PEP numbers that this PEP depends on. PEPs may also have a Replaced-By: header indicating that a PEP has been rendered obsolete by a later document; the value is the number of the PEP that replaces the current document. The newer PEP must have a Replaces: header containing the number of the PEP that it rendered obsolete. PEP Formatting Requirements PEP headings must begin in column zero and the initial letter of each word must be capitalized as in book titles. Acronyms should be in all capitals. The body of each section must be indented 4 spaces. Code samples inside body sections should be indented a further 4 spaces, and other indentation can be used as required to make the text readable. You must use two blank lines between the last line of a section's body and the next section heading. You must adhere to the Emacs convention of adding two spaces at the end of every sentence. You should fill your paragraphs to column 70, but under no circumstances should your lines extend past column 79. If your code samples spill over column 79, you should rewrite them. Tab characters must never appear in the document at all. A PEP should include the standard Emacs stanza included by example at the bottom of this PEP. A PEP must contain a Copyright section, and it is strongly recommended to put the PEP in the public domain. When referencing an external web page in the body of a PEP, you should include the title of the page in the text, with a footnote reference to the URL. Do not include the URL in the body text of the PEP. E.g. Refer to the Python Language web site [1] for more details. ... [1] http://www.python.org When referring to another PEP, include the PEP number in the body text, such as "PEP 1". The title may optionally appear. Add a footnote reference that includes the PEP's title and author. It may optionally include the explicit URL on a separate line, but only in the References section. Note that the pep2html.py script will calculate URLs automatically, e.g.: ... Refer to PEP 1 [7] for more information about PEP style ... References [7] PEP 1, PEP Purpose and Guidelines, Warsaw, Hylton http://www.python.org/peps/pep-0001.html If you decide to provide an explicit URL for a PEP, please use this as the URL template: http://www.python.org/peps/pep-xxxx.html PEP numbers in URLs must be padded with zeros from the left, so as to be exactly 4 characters wide, however PEP numbers in text are never padded. Reporting PEP Bugs, or Submitting PEP Updates How you report a bug, or submit a PEP update depends on several factors, such as the maturity of the PEP, the preferences of the PEP author, and the nature of your comments. For the early draft stages of the PEP, it's probably best to send your comments and changes directly to the PEP author. For more mature, or finished PEPs you may want to submit corrections to the SourceForge bug manager[6] or better yet, the SourceForge patch manager[2] so that your changes don't get lost. If the PEP author is a SF developer, assign the bug/patch to him, otherwise assign it to the PEP editor. When in doubt about where to send your changes, please check first with the PEP author and/or PEP editor. PEP authors who are also SF committers, can update the PEPs themselves by using "cvs commit" to commit their changes. Remember to also push the formatted PEP text out to the web by doing the following: % python pep2html.py -i NUM where NUM is the number of the PEP you want to push out. See % python pep2html.py --help for details. Transferring PEP Ownership It occasionally becomes necessary to transfer ownership of PEPs to a new champion. In general, we'd like to retain the original author as a co-author of the transferred PEP, but that's really up to the original author. A good reason to transfer ownership is because the original author no longer has the time or interest in updating it or following through with the PEP process, or has fallen off the face of the 'net (i.e. is unreachable or not responding to email). A bad reason to transfer ownership is because you don't agree with the direction of the PEP. We try to build consensus around a PEP, but if that's not possible, you can always submit a competing PEP. If you are interested assuming ownership of a PEP, send a message asking to take over, addressed to both the original author and the PEP editor <peps(a)python.org>. If the original author doesn't respond to email in a timely manner, the PEP editor will make a unilateral decision (it's not like such decisions can be reversed. :). References and Footnotes [1] This historical record is available by the normal CVS commands for retrieving older revisions. For those without direct access to the CVS tree, you can browse the current and past PEP revisions via the SourceForge web site at http://cvs.sourceforge.net/cgi-bin/cvsweb.cgi/python/nondist/peps/?cvsroot=… [2] http://sourceforge.net/tracker/?group_id=5470&atid=305470 [3] http://sourceforge.net/tracker/?atid=355470&group_id=5470&func=browse [4] http://www.opencontent.org/openpub/ [5] The script referred to here is pep2html.py, which lives in the same directory in the CVS tree as the PEPs themselves. Try "pep2html.py --help" for details. The URL for viewing PEPs on the web is http://www.python.org/peps/ [6] http://sourceforge.net/tracker/?group_id=5470&atid=305470 [7] PEP 9, Sample PEP Template http://www.python.org/peps/pep-0009.html Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil sentence-end-double-space: t fill-column: 70 End:

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RE: [Python-Dev] Those import related syntax errors again...
by Samuele Pedroni Feb. 23, 2005

Feb. 23, 2005

Hi. [Mark Hammond] > The point isn't about my suffering as such. The point is more that > python-dev owns a tiny amount of the code out there, and I don't believe we > should put Python's users through this. > > Sure - I would be happy to "upgrade" all the win32all code, no problem. I > am also happy to live in the bleeding edge and take some pain that will > cause. > > The issue is simply the user base, and giving Python a reputation of not > being able to painlessly upgrade even dot revisions. I agree with all this. [As I imagined explicit syntax did not catch up and would require lot of discussions.] [GvR] > > Another way is to use special rules > > (similar to those for class defs), e.g. having > > > > <frag> > > y=3 > > def f(): > > exec "y=2" > > def g(): > > return y > > return g() > > > > print f() > > </frag> > > > > # print 3. > > > > Is that confusing for users? maybe they will more naturally expect 2 > > as outcome (given nested scopes). > > This seems the best compromise to me. It will lead to the least > broken code, because this is the behavior that we had before nested > scopes! It is also quite easy to implement given the current > implementation, I believe. > > Maybe we could introduce a warning rather than an error for this > situation though, because even if this behavior is clearly documented, > it will still be confusing to some, so it is better if we outlaw it in > some future version. > Yes this can be easy to implement but more confusing situations can arise: <frag> y=3 def f(): y=9 exec "y=2" def g(): return y return y,g() print f() </frag> What should this print? the situation leads not to a canonical solution as class def scopes. or <frag> def f(): from foo import * def g(): return y return g() print f() </frag> [Mark Hammond] > > This probably won't be a very popular suggestion, but how about pulling > > nested scopes (I assume they are at the root of the problem) > > until this can be solved cleanly? > > Agreed. While I think nested scopes are kinda cool, I have lived without > them, and really without missing them, for years. At the moment the cure > appears worse then the symptoms in at least a few cases. If nothing else, > it compromises the elegant simplicity of Python that drew me here in the > first place! > > Assuming that people really _do_ want this feature, IMO the bar should be > raised so there are _zero_ backward compatibility issues. I don't say anything about pulling nested scopes (I don't think my opinion can change things in this respect) but I should insist that without explicit syntax IMO raising the bar has a too high impl cost (both performance and complexity) or creates confusion. [Andrew Kuchling] > >Assuming that people really _do_ want this feature, IMO the bar should be > >raised so there are _zero_ backward compatibility issues. > > Even at the cost of additional implementation complexity? At the cost > of having to learn "scopes are nested, unless you do these two things > in which case they're not"? > > Let's not waffle. If nested scopes are worth doing, they're worth > breaking code. Either leave exec and from..import illegal, or back > out nested scopes, or think of some better solution, but let's not > introduce complicated backward compatibility hacks. IMO breaking code would be ok if we issue warnings today and implement nested scopes issuing errors tomorrow. But this is simply a statement about principles and raised impression. IMO import * in an inner scope should end up being an error, not sure about 'exec's. We will need a final BDFL statement. regards, Samuele Pedroni.

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RE: [Spambayes] Question (or possibly a bug report)
by Meyer, Tony Aug. 31, 2003

Aug. 31, 2003

> So when the marshalled representation of 0.001 is loaded under > "german" LC_NUMERIC here, we get back exactly 0.0. I'm not > sure why. When I call "marshal.dumps(0.1)" from AsyncDialog (or anywhere in the Outlook code) I get "f\x030.0", which fits with what you have. > So the obvious <wink> answers are: (Glad you posted this - I was wading through the progress of marshalling (PyOS_snprintf etc) and getting rapidly lost). > 1. When LC_NUMERIC is "german", MS C's atof() stops at the first > period it sees. This is the case: """ #include <locale.h> #include <stdio.h> #include <stdlib.h> int main() { float f; setlocale(LC_NUMERIC, "german"); f = atof("0.1"); printf("%f\n", f); } """ Gives me with gcc version 3.2 20020927 (prerelease): 0.100000 Gives me with Microsoft C++ Builder (I don't have Visual C++ handy, but I suppose it would be the same): 0,00000 The help file for Builder does say that this is the correct behaviour - it will stop when it finds an unrecognised character - here '.' is unrecognised (because we are in German), so it stops. Does this then mean that this is a Python bug? Or because Python tells us not to change the c locale and we (Outlook) are, it's our fault/problem? Presumably what we'll have to do for a solution is just what Mark is doing now - find the correct place to put a call that (re)sets the c locale to English. =Tony Meyer

7 15

RELEASED Python 2.3 (final)
by barry＠python.org Aug. 9, 2003

Aug. 9, 2003

On behalf of the Python development team and the Python community, I'm happy to announce the release of Python 2.3 (final). Nineteen months in the making, Python 2.3 represents a commitment to stability and improved performance, with a minimum of new language features. Countless bugs and memory leaks have been fixed, many new and updated modules have been added, and the new type/class system introduced in Python 2.2 has been significantly improved. Python 2.3 can be up to 30% faster than Python 2.2. For more information on Python 2.3, including download links for various platforms, release notes, and known issues, please see: http://www.python.org/2.3 Highlights of this new release include: - A brand new version of IDLE, the Python IDE, from the IDLEfork project at SourceForge. - Many new and improved library modules including: sets, heapq, datetime, textwrap, optparse, logging, bsddb, bz2, tarfile, ossaudiodev, itertools, platform, csv, timeit, shelve, DocXMLRPCServer, imaplib, imp, trace, and a new random number generator based on the highly acclaimed Mersenne Twister algorithm (with a period of 2**19937-1). Some obsolete modules have been deprecated. - New and improved built-ins including: o enumerate(): an iterator yielding (index, item) pairs o sum(): a new function to sum a sequence of numbers o basestring: an abstract base string type for str and unicode o bool: a proper type with instances True and False o compile(), eval(), exec: fully support Unicode, and allow input not ending in a newline o range(): support for long arguments (magnitude > sys.maxint) o dict(): new constructor signatures o filter(): returns Unicode when the input is Unicode o int() can now return long o isinstance(), super(): Now support instances whose type() is not equal to their __class__. super() no longer ignores data descriptors, except for __class__. o raw_input(): can now return Unicode objects o slice(), buffer(): are now types rather than functions - Many new doctest extensions, allowing them to be run by unittest. - Extended slices, e.g. "hello"[::-1] returns "olleh". - Universal newlines mode for reading files (converts \r, \n and \r\n all into \n). - Source code encoding declarations. (PEP 263) - Import from zip files. (PEP 273 and PEP 302) - FutureWarning issued for "unsigned" operations on ints. (PEP 237) - Faster list.sort() is now stable. - Unicode filenames on Windows. (PEP 227) - Karatsuba long multiplication (running time O(N**1.58) instead of O(N**2)). - pickle, cPickle, and copy support a new pickling protocol for more efficient pickling of (especially) new-style class instances. - The socket module now supports optional timeouts on all operations. - ssl support has been incorporated into the Windows installer. - Many improvements to Tkinter. Python 2.3 contains many other improvements, including the adoption of many Python Enhancement Proposals (PEPs). For details see: http://www.python.org/2.3/highlights.html Enjoy. happy-50th-birthday-geddy-ly y'rs, -Barry Barry Warsaw barry(a)python.org Python 2.3 Release Manager (and the PythonLabs team: Tim, Fred, Jeremy, and Guido)

10 13

2.3b1 release
by Guido van Rossum Aug. 8, 2003

Aug. 8, 2003

I'd like to do a 2.3b1 release someday. Maybe at the end of next week, that would be Friday April 25. If anyone has something that needs to be done before this release go out, please let me know! Assigning a SF bug or patch to me and setting the priority to 7 is a good way to get my attention. --Guido van Rossum (home page: http://www.python.org/~guido/)

14 51

Looking for programs using regular expressions
by Scott A Crosby Aug. 1, 2003

Aug. 1, 2003

I'm working on techniques to automatically identify problematic regular expressions where carefully chosen inputs can cause a matcher to run for a long time. I need testcases, so I'm looking for Python software that that is widely used and also uses lots of regular expressions. Can anyone offer any suggestions of what I should look at? I'm also looking for Perl software. Thanks Scott I'm not on the list, so please CC me any replies.

4 3

Looking for a couple Emacs Lisp helper/guru types
by Skip Montanaro Aug. 1, 2003

Aug. 1, 2003

Barry & Ken have run completely out of round tuits on which are written "python-mode". I believe Barry indicated privately that he is going to set up a SF project to allow other folks to contribute (maybe he's just going to give Python CVS developer privileges to anyone, he may be just that giddy after the 2.3 release). I have very little time as well and have very old, feeble Emacs Lisp skills to boot. Hell, I can't even get my Python files to save properly with tramp these days, and I never did like mapcar. I'm sure Barry will announce here and probably on c.l.py once the project's available, but in anticipation of that, if you are an Emacs or XEmacs person who uses python mode, please consider getting reacquainted with your inner functional self. Your parens will be so proud. Skip

2 1

A syntax for function attributes?
by Pat Miller Aug. 1, 2003

Aug. 1, 2003

Michael wrote: > I don't object to a syntax for function attributes... in fact, I've seen no > specific proposal to object to. But I find your point above HIGHLY > unconvincing: I agree that def sqr(x): return x*x sqr.inline = true is about the same length as def sqr [inline=true](x): return x*x But when this function is 60 lines long rather than 2 lines long, the association is broken. This is my major objection, not the number of characters I write, but rather the number of lines I must scan. People wouldn't be as likely to use doc strings if the syntax was: def function(x): code code code code function.__doc__ = "this is my doc string" > Notice that this is the approach that Guido used for classmethod and > its ilk, and we're still working out what the right "special syntax" I use the classmethod call because its the only (good) way to do the task, but I have the same objection. When I write class Foo: def method(self, ...): ... method = classmethod(method) Upon reading, I don't find out the "true meaning" of the method until I happen upon the classmethod call. Even in C++ with its bogus syntax, I can identify a class method at the point of definition class Foo { static void method(...); ... } so, it would be nice if there was a way to densely associate the information at the point of function definition just as the doc string is densely associated with the function definition. class Foo: def method [classmethod=true](self, ...): "doc string" def get_x [property="x"](self): return self.__x -- Patrick Miller | (925) 423-0309 | http://www.llnl.gov/CASC/people/pmiller The more original a discovery, the more obvious it seems afterward. -- Arthur Koestler

9 10

Switch to 2.4a0 on trunk?
by Mark Hammond Aug. 1, 2003

Aug. 1, 2003

I notice that parts of the trunk are reporting themselves as Python 2.4, but other key parts for Windows are still Python 2.3 - eg, the DLL name, the PC\*.rc files, etc. Should I check code in to move everything to a 2.4 world on the trunk? And while I am asking, I am a little uncertain about the CVS tags. Can someone explain the distinction between release23-branch and release23-fork for me? Is there a branch that will track the "latest 2.3" for the next few years (ie, through 2.3.1, 2.3.2 etc?) Thanks, Mark.

8 10

deadlock problem
by Harri Pasanen Aug. 1, 2003

Aug. 1, 2003

Hi, I'm having a deadlock on import in my embedded python 2.3rc2, on Win2000, built with Visual C++ 7.1. Having spent a fair amount of time going through the code, and various threads, it is still not clear to me if I'm hitting the problem described in the thread: http://mail.python.org/pipermail/python-dev/2003-February/033436.html or if I'm triggering it because of something else alltogether, as I'm only seeing the problem on Win2000, on Linux it works fine. Basically my code does this in one C level thread: PyGILState_STATE _tstate = PyGILState_Ensure (); PyObject* usermod = PyImport_ImportModule ("echo"); Where echo.py is just: print "ECHO" import time time.sleep(1) print "DONE" It never prints out "DONE". If I take away the sleep(), it finishes, printing DONE. running with THREADDEBUG=15, I'm getting the output below, and the last two lines leave me utterly puzzled, as if something would be quite wrong on my machine (Win2000 under VmWare Linux host). Why could the same thread be unable reacquire a lock it just held? PyThread_init_thread called 1084: PyThread_allocate_lock() -> 01647578 1084: PyThread_acquire_lock(01647578, 1) called 1084: PyThread_acquire_lock(01647578, 1) -> 1 1084: PyThread_release_lock(01647578) called 1084: PyThread_acquire_lock(01647578, 1) called 1084: PyThread_acquire_lock(01647578, 1) -> 1 1084: PyThread_release_lock(01647578) called PyThread_allocate_lock called 1084: PyThread_allocate_lock() -> 0164A280 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called PyThread_allocate_lock called 1084: PyThread_allocate_lock() -> 0256DD40 1084: PyThread_acquire_lock(0256DD40, 1) called 1084: PyThread_acquire_lock(0256DD40, 1) -> 1 1084: PyThread_release_lock(0256DD40) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called PyThread_allocate_lock called 1084: PyThread_allocate_lock() -> 01648DA8 1084: PyThread_acquire_lock(01648DA8, 1) called 1084: PyThread_acquire_lock(01648DA8, 1) -> 1 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_release_lock(01648DA8) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 1084: PyThread_release_lock(0164A280) called 1084: PyThread_acquire_lock(0164A280, 0) called 1084: PyThread_acquire_lock(0164A280, 0) -> 1 ECHO 1084: PyThread_release_lock(01648DA8) called 1084: PyThread_acquire_lock(01648DA8, 1) called Harri

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