Mailman 3 March 2009 - Python-Dev

PEP 1, PEP Purpose and Guidelines
by barry＠zope.com 18 May '21

18 May '21

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:

8 14

Reviving restricted mode?
by Guido van Rossum 14 Aug '14

14 Aug '14

I've received some enthusiastic emails from someone who wants to revive restricted mode. He started out with a bunch of patches to the CPython runtime using ctypes, which he attached to an App Engine bug: http://code.google.com/p/googleappengine/issues/detail?id=671 Based on his code (the file secure.py is all you need, included in secure.tar.gz) it seems he believes the only security leaks are __subclasses__, gi_frame and gi_code. (I have since convinced him that if we add "restricted" guards to these attributes, he doesn't need the functions added to sys.) I don't recall the exploits that Samuele once posted that caused the death of rexec.py -- does anyone recall, or have a pointer to the threads? -- --Guido van Rossum (home page: http://www.python.org/~guido/)

19 35

pthreads, fork, import, and execvp
by Rotem Yaari 17 Sep '09

17 Sep '09

Hello everyone! We have been encountering several deadlocks in a threaded Python application which calls subprocess.Popen (i.e. fork()) in some of its threads. This has occurred on Python 2.4.1 on a 2.4.27 Linux kernel. Preliminary analysis of the hang shows that the child process blocks upon entering the execvp function, in which the import_lock is acquired due to the following line: def _ execvpe(file, args, env=None): from errno import ENOENT, ENOTDIR ... It is known that when forking from a pthreaded application, acquisition attempts on locks which were already locked by other threads while fork() was called will deadlock. Due to these oddities we were wondering if it would be better to extract the above import line from the execvpe call, to prevent lock acquisition attempts in such cases. Another workaround could be re-assigning a new lock to import_lock (such a thing is done with the global interpreter lock) at PyOS_AfterFork or pthread_atfork. We'd appreciate any opinions you might have on the subject. Thanks in advance, Yair and Rotem

12 29

compiling python2.5 on linux under wine
by Luke Kenneth Casson Leighton 08 Sep '09

08 Sep '09

hey, has anyone investigated compiling python2.5 using winegcc, under wine? i'm presently working my way through it, just for kicks, and was wondering if anyone would like to pitch in or stare at the mess under a microscope. it's not as crazed as it sounds. cross-compiling python2.5 for win32 with mingw32 is an absolute miserable bitch of a job that goes horribly wrong when you actually try to use the minimalist compiler to do any real work. so i figured that it would be easier to get python compiled using wine. i _have_ got some success - a python script and a python.exe.so (which is winegcc's friendly way of telling you you have something that stands a chance of working) as well as a libpython25.dll.so. what i _don't_ yet have is an _md5.dll (or should it be _md5.lib?) i.e. the standard modules are a bit... iffy. the _winreg.o is compiled; the _md5.o is compiled; the winreg.lib is not. whoops. plus, it's necessary to enable nt_dl.c which is in PC/ _not_ in Modules/. one of the key issues that's a bit of a bitch is that python is compiled up for win32 with a hard-coded pyconfig.h which someone went to a _lot_ of trouble to create by hand instead of using autoconf. oh - and it uses visualstudio so there's not even a Makefile. ignoring that for the time-being was what allowed me to get as far as actually having a python interpreter (with no c-based modules). so there's a whole _stack_ of stuff that needs dragging kicking and screaming into the 21st century. there _is_ a reason why i want to do this. actually, there's two. firstly, i sure as shit do _not_ want to buy, download, install _or_ run visual studio. i flat-out refuse to run an MS os and visual studio runs like a dog under wine. secondly, i want a python25.lib which i can use to cross-compile modules for poor windows users _despite_ sticking to my principles and keeping my integrity as a free software developer. thirdly i'd like to cross-compile pywebkitgtk for win32 fourthly i'd like to compile and link applications to the extremely successful and well wicked MSHTML.DLL... in the _wine_ project :) not the one in windows (!) i want to experiment with DOM model manipulation - from python - similar to the OLPC HulaHop project - _but_ i want to compile or cross-compile everything from linux, not windows (see 1 above) fifthly i'd like to see COM (DCOM) working and pywin32 compiled and useable under wine, even if it means having to get a license to use dcom98 and oleauth.lib and oleauth.h etc. and all the developer files needed to link DCOM applications under windows. actually what i'd _really_ like to see is FreeDCE's DCOM work actually damn well finished, it's only been eight years since wez committed the first versions of the IDL and header files, and it's only been over fifteen years since microsoft began its world domination using COM and DCOM. ... but that's another story :) so that's ... five reasons not two. if anyone would like to collaborate on a crazed project with someone who can't count, i'm happy to make available what i've got up to so far, on github.org. l.

6 12

GSoC: Core Python development tools
by Daniel (ajax) Diniz 23 Jul '09

23 Jul '09

Hi, I'd like to bring up the general idea of using a PSF slot in GSoC2009 to improve the Python development infrastructure. I also happen to have two concrete proposals for that (such a coincidence!). But I assure you the general idea is more important than my proposals :) General: Solving issues that get in core devs' way when they work on Python development could be a nice PSF GSoC project. I believe there are enough code related tasks that would greatly improve Python development workflow but lack manpower to complete. E.g., ISTM that a student working on svnmerge in past SoC editions would've been able to mitigate some painful shortcomings. If the core developers could come up with a list of peeves that would be solvable in code (in existing tools), that would allow for a very useful GSoC proposal. Proposals: These might fit the description above, and they're both tracker related (yep, one-trick-pony here). The upside is that at least one potential mentor is available for each, and I'd be able to offer support to the student. First, the PSF could invest a slot on integrating different tools of the development workflow. Variations of 'file issue at bug tracker, submit code for review' or 'branch locally to virtualenv, upload failing testcase to tracker, upload patch to tracker' command line utils. If these could be developed as general tools (i.e., not deeply tied to Python dev infrastructure), Ali Afshar from PIDA is willing to mentor it. I'd be available to help with Roundup and Rietveld (integration in progress), but would like to see it work with Launchpad, Bugzilla, Google Code and Review Board :) The other proposal is to use a slot in Roundup proper and the Python tracker instance. This could have a core Roundup developer as mentor, under the condition it's focused on Roundup itself. IMO, are some missing/broken core features in Roundup that would have a positive impact on our tracker, mostly those relating to searches, security and UI. I'd have a lot to contribute to the Python tracker part, based on ongoing work. Even if neither is considered worthy, I'll keep them on my to-do list and hope to slowly and hackishly work towards both proposals' goals. Barring feedback saying that they're out of scope, stupid and downright offensive, I'll post details on each to this thread very soon. So, if the PSF was to use a slot on improving the way you work on Python development, what would you like to see fixed or implemented? Best regards, Daniel

13 31

Re: subprocess and EINTR errnos
by Peter Astrand 07 Jul '09

07 Jul '09

On Wed, 10 Nov 2004, John P Speno wrote: Hi, sorry for the delayed response. > While using subprocess (aka popen5), I came across one potential gotcha. I've had > exceptions ending like this: > > File "test.py", line 5, in test > cmd = popen5.Popen(args, stdout=PIPE) > File "popen5.py", line 577, in __init__ > data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB > OSError: [Errno 4] Interrupted system call > > (on Solaris 9) > > Would it make sense for subprocess to use a more robust read() function > which can handle these cases, i.e. when the parent's read on the pipe > to the child's stderr is interrupted by a system call, and returns EINTR? > I imagine it could catch EINTR and EAGAIN and retry the failed read(). I assume you are using signals in your application? The os.read above is not the only system call that can fail with EINTR. subprocess.py is full of other system calls that can fail, and I suspect that many other Python modules are as well. I've made a patch (attached) to subprocess.py (and test_subprocess.py) that should guard against EINTR, but I haven't committed it yet. It's quite large. Are Python modules supposed to handle EINTR? Why not let the C code handle this? Or, perhaps the signal module should provide a sigaction function, so that users can use SA_RESTART. Index: subprocess.py =================================================================== RCS file: /cvsroot/python/python/dist/src/Lib/subprocess.py,v retrieving revision 1.8 diff -u -r1.8 subprocess.py --- subprocess.py 7 Nov 2004 14:30:34 -0000 1.8 +++ subprocess.py 17 Nov 2004 19:42:30 -0000 @@ -888,6 +888,50 @@ pass + def _read_no_intr(self, fd, buffersize): + """Like os.read, but retries on EINTR""" + while True: + try: + return os.read(fd, buffersize) + except OSError, e: + if e.errno == errno.EINTR: + continue + else: + raise + + + def _read_all(self, fd, buffersize): + """Like os.read, but retries on EINTR, and reads until EOF""" + all = "" + while True: + data = self._read_no_intr(fd, buffersize) + all += data + if data == "": + return all + + + def _write_no_intr(self, fd, s): + """Like os.write, but retries on EINTR""" + while True: + try: + return os.write(fd, s) + except OSError, e: + if e.errno == errno.EINTR: + continue + else: + raise + + def _waitpid_no_intr(self, pid, options): + """Like os.waitpid, but retries on EINTR""" + while True: + try: + return os.waitpid(pid, options) + except OSError, e: + if e.errno == errno.EINTR: + continue + else: + raise + def _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, @@ -963,7 +1007,7 @@ exc_value, tb) exc_value.child_traceback = ''.join(exc_lines) - os.write(errpipe_write, pickle.dumps(exc_value)) + self._write_no_intr(errpipe_write, pickle.dumps(exc_value)) # This exitcode won't be reported to applications, so it # really doesn't matter what we return. @@ -979,7 +1023,7 @@ os.close(errwrite) # Wait for exec to fail or succeed; possibly raising exception - data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB + data = self._read_all(errpipe_read, 1048576) # Exceptions limited to 1 MB os.close(errpipe_read) if data != "": child_exception = pickle.loads(data) @@ -1003,7 +1047,7 @@ attribute.""" if self.returncode == None: try: - pid, sts = os.waitpid(self.pid, os.WNOHANG) + pid, sts = self._waitpid_no_intr(self.pid, os.WNOHANG) if pid == self.pid: self._handle_exitstatus(sts) except os.error: @@ -1015,7 +1059,7 @@ """Wait for child process to terminate. Returns returncode attribute.""" if self.returncode == None: - pid, sts = os.waitpid(self.pid, 0) + pid, sts = self._waitpid_no_intr(self.pid, 0) self._handle_exitstatus(sts) return self.returncode @@ -1049,27 +1093,33 @@ stderr = [] while read_set or write_set: - rlist, wlist, xlist = select.select(read_set, write_set, []) + try: + rlist, wlist, xlist = select.select(read_set, write_set, []) + except select.error, e: + if e[0] == errno.EINTR: + continue + else: + raise if self.stdin in wlist: # When select has indicated that the file is writable, # we can write up to PIPE_BUF bytes without risk # blocking. POSIX defines PIPE_BUF >= 512 - bytes_written = os.write(self.stdin.fileno(), input[:512]) + bytes_written = self._write_no_intr(self.stdin.fileno(), input[:512]) input = input[bytes_written:] if not input: self.stdin.close() write_set.remove(self.stdin) if self.stdout in rlist: - data = os.read(self.stdout.fileno(), 1024) + data = self._read_no_intr(self.stdout.fileno(), 1024) if data == "": self.stdout.close() read_set.remove(self.stdout) stdout.append(data) if self.stderr in rlist: - data = os.read(self.stderr.fileno(), 1024) + data = self._read_no_intr(self.stderr.fileno(), 1024) if data == "": self.stderr.close() read_set.remove(self.stderr) Index: test/test_subprocess.py =================================================================== RCS file: /cvsroot/python/python/dist/src/Lib/test/test_subprocess.py,v retrieving revision 1.14 diff -u -r1.14 test_subprocess.py --- test/test_subprocess.py 12 Nov 2004 15:51:48 -0000 1.14 +++ test/test_subprocess.py 17 Nov 2004 19:42:30 -0000 @@ -7,6 +7,7 @@ import tempfile import time import re +import errno mswindows = (sys.platform == "win32") @@ -35,6 +36,16 @@ fname = tempfile.mktemp() return os.open(fname, os.O_RDWR|os.O_CREAT), fname + def read_no_intr(self, obj): + while True: + try: + return obj.read() + except IOError, e: + if e.errno == errno.EINTR: + continue + else: + raise + # # Generic tests # @@ -123,7 +134,7 @@ p = subprocess.Popen([sys.executable, "-c", 'import sys; sys.stdout.write("orange")'], stdout=subprocess.PIPE) - self.assertEqual(p.stdout.read(), "orange") + self.assertEqual(self.read_no_intr(p.stdout), "orange") def test_stdout_filedes(self): # stdout is set to open file descriptor @@ -151,7 +162,7 @@ p = subprocess.Popen([sys.executable, "-c", 'import sys; sys.stderr.write("strawberry")'], stderr=subprocess.PIPE) - self.assertEqual(remove_stderr_debug_decorations(p.stderr.read()), + self.assertEqual(remove_stderr_debug_decorations(self.read_no_intr(p.stderr)), "strawberry") def test_stderr_filedes(self): @@ -186,7 +197,7 @@ 'sys.stderr.write("orange")'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT) - output = p.stdout.read() + output = self.read_no_intr(p.stdout) stripped = remove_stderr_debug_decorations(output) self.assertEqual(stripped, "appleorange") @@ -220,7 +231,7 @@ stdout=subprocess.PIPE, cwd=tmpdir) normcase = os.path.normcase - self.assertEqual(normcase(p.stdout.read()), normcase(tmpdir)) + self.assertEqual(normcase(self.read_no_intr(p.stdout)), normcase(tmpdir)) def test_env(self): newenv = os.environ.copy() @@ -230,7 +241,7 @@ 'sys.stdout.write(os.getenv("FRUIT"))'], stdout=subprocess.PIPE, env=newenv) - self.assertEqual(p.stdout.read(), "orange") + self.assertEqual(self.read_no_intr(p.stdout), "orange") def test_communicate(self): p = subprocess.Popen([sys.executable, "-c", @@ -305,7 +316,8 @@ 'sys.stdout.write("\\nline6");'], stdout=subprocess.PIPE, universal_newlines=1) - stdout = p.stdout.read() + + stdout = self.read_no_intr(p.stdout) if hasattr(open, 'newlines'): # Interpreter with universal newline support self.assertEqual(stdout, @@ -343,7 +355,7 @@ def test_no_leaking(self): # Make sure we leak no resources - max_handles = 1026 # too much for most UNIX systems + max_handles = 10 # too much for most UNIX systems if mswindows: max_handles = 65 # a full test is too slow on Windows for i in range(max_handles): @@ -424,7 +436,7 @@ 'sys.stdout.write(os.getenv("FRUIT"))'], stdout=subprocess.PIPE, preexec_fn=lambda: os.putenv("FRUIT", "apple")) - self.assertEqual(p.stdout.read(), "apple") + self.assertEqual(self.read_no_intr(p.stdout), "apple") def test_args_string(self): # args is a string @@ -457,7 +469,7 @@ p = subprocess.Popen(["echo $FRUIT"], shell=1, stdout=subprocess.PIPE, env=newenv) - self.assertEqual(p.stdout.read().strip(), "apple") + self.assertEqual(self.read_no_intr(p.stdout).strip(), "apple") def test_shell_string(self): # Run command through the shell (string) @@ -466,7 +478,7 @@ p = subprocess.Popen("echo $FRUIT", shell=1, stdout=subprocess.PIPE, env=newenv) - self.assertEqual(p.stdout.read().strip(), "apple") + self.assertEqual(self.read_no_intr(p.stdout).strip(), "apple") def test_call_string(self): # call() function with string argument on UNIX @@ -525,7 +537,7 @@ p = subprocess.Popen(["set"], shell=1, stdout=subprocess.PIPE, env=newenv) - self.assertNotEqual(p.stdout.read().find("physalis"), -1) + self.assertNotEqual(self.read_no_intr(p.stdout).find("physalis"), -1) def test_shell_string(self): # Run command through the shell (string) @@ -534,7 +546,7 @@ p = subprocess.Popen("set", shell=1, stdout=subprocess.PIPE, env=newenv) - self.assertNotEqual(p.stdout.read().find("physalis"), -1) + self.assertNotEqual(self.read_no_intr(p.stdout).find("physalis"), -1) def test_call_string(self): # call() function with string argument on Windows /Peter Åstrand <astrand(a)lysator.liu.se>

5 5

Evaluated cmake as an autoconf replacement
by Jeffrey Yasskin 13 Apr '09

13 Apr '09

I've heard some good things about cmake — LLVM, googletest, and Boost are all looking at switching to it — so I wanted to see if we could simplify our autoconf+makefile system by using it. The biggest wins I see from going to cmake are: 1. It can autogenerate the Visual Studio project files instead of needing them to be maintained separately 2. It lets you write functions and modules without understanding autoconf's mix of shell and M4. 3. Its generated Makefiles track header dependencies accurately so we might be able to add private headers efficiently. However, after trying it out during PyCon and looking over the previous attempt at <http://mail.python.org/pipermail/python-dev/2007-July/073912.html>, I can't recommend switching to it. A. It has no equivalent of autoheader, so we'd have to maintain pyconfig.h.in by hand. B. It does not allow the CMakeLists.txt file control the --help output. This appears to be an intentional decision (http://www.cmake.org/pipermail/cmake-promote/2006-May/000095.html). To replace it, they have an interactive mode (which asks you about each possible option) and a -LH flag (which runs the whole configure process and then tells you about the flags you could have set if you knew about them). C. It does not allow the CMakeLists.txt file to see the command line, so we can't stay backward compatible with the configure script, and we'd have to replace flags like --with-pydebug with -Dpydebug:bool=true. We could write a separate configure script to mitigate this and the previous problem, but we'd have to keep that in sync with CMakeLists.txt manually. D. It doesn't have an expression language, so to replace ac_md_system=`echo $ac_sys_system | tr -d '[/ ]' | tr '[[A-Z]]' '[[a-z]]'` you have to write: string(REGEX REPLACE "[/ ]" "" ac_md_system ${ac_sys_system}) string(TOLOWER ${ac_md_system} ac_md_system) So, at the very least, it doesn't look like a big enough win to justify switching, and may not be a win at all. The other popular configure+make replacement is scons. The biggest objection to scons before even looking at it is that it requires a working Python interpreter in order to build Python, causing a bootstrap problem. However, Brett Cannon and I talked, and we think this is surmountable. First, nearly every desktop system comes with a Python interpreter, which would avoid the bootstrap for ordinary development. Second, we need a cross compilation story anyway for embedded systems, and the same mechanism could be used to get Python onto a new desktop platform. Third, Jython and IronPython are pretty mature and either can run scons now or should be able to run it after some relatively easy tweaks. They could be used to build CPython on a new platform. I don't intend to look into scons myself any time soon, but I'd be interested in anyone's experiences who does try it. Jeffrey

16 41

pyc files, constant folding and borderline portability issues
by Antoine Pitrou 08 Apr '09

08 Apr '09

Hello, There are a couple of ancillary portability concerns due to optimizations which store system-dependent results of operations between constants in pyc files: - Issue #5057: code like '\U00012345'[0] is optimized away and its result stored as a constant in the pyc file, but the result should be different in UCS-2 and UCS-4 builds. - Issue #5593: code like 1e16+2.9999 is optimized away and its result stored as a constant (again), but the result can vary slightly depending on the internal FPU precision. These problems have probably been there for a long time and almost no one seems to complain, but I thought I'd report them here just in case. Regards Antoine.

11 24

os.defpath for Windows
by Yinon Ehrlich 07 Apr '09

07 Apr '09

Hi, just saw that os.defpath for Windows is defined as Lib/ntpath.py:30:defpath = '.;C:\\bin' Most Windows machines I saw has no c:\bin directory. Any reason why it was defined this way ? Thanks, Yinon

2 2

deprecating BaseException.message
by Brett Cannon 07 Apr '09

07 Apr '09

During the PyCon sprint I tried to make BaseException accept only a single argument and bind it to BaseException.message . I was successful (see the p3yk_no_args_on_exc branch), but it was very painful to pull off as anyone who sat around me the last three days of the sprint will tell you as they had to listen to me curse incessantly. Because of the pain that I went through in the transition and thus the lessons learned, Guido and I discussed it and we think it would be best to give up on forcing BaseException to accept only a single argument. I think it is still doable, but requires a multi-release transition period and not the one that 2.6 -> 3.0 is offering. And so Guido and I plan on deprecating BaseException.message as its entire point in existence was to help transition to what we are not going to have happen. =) Now that means BaseException.message might hold the record for shortest lived feature as it was only introduced in 2.5 and is now to be deprecated in 2.6 and removed in 2.7/3.0. =) Below is PEP 352, revised to reflect the removal of BaseException.messageand for letting the 'args' attribute stay (along with suggesting one should only pass a single argument to BaseException). Basically the interface for exceptions doesn't really change in 3.0 except for the removal of __getitem__. -------------------------------------------------------------------------- PEP: 352 Title: Required Superclass for Exceptions Version: $Revision: 53592 $ Last-Modified: $Date: 2007-01-28 21:54:11 -0800 (Sun, 28 Jan 2007) $ Author: Brett Cannon <brett(a)python.org> Guido van Rossum <guido(a)python.org> Status: Final Type: Standards Track Content-Type: text/x-rst Created: 27-Oct-2005 Post-History: Abstract ======== In Python 2.4 and before, any (classic) class can be raised as an exception. The plan for 2.5 was to allow new-style classes, but this makes the problem worse -- it would mean *any* class (or instance) can be raised! This is a problem as it prevents any guarantees from being made about the interface of exceptions. This PEP proposes introducing a new superclass that all raised objects must inherit from. Imposing the restriction will allow a standard interface for exceptions to exist that can be relied upon. It also leads to a known hierarchy for all exceptions to adhere to. One might counter that requiring a specific base class for a particular interface is unPythonic. However, in the specific case of exceptions there's a good reason (which has generally been agreed to on python-dev): requiring hierarchy helps code that wants to *catch* exceptions by making it possible to catch *all* exceptions explicitly by writing ``except BaseException:`` instead of ``except *:``. [#hierarchy-good]_ Introducing a new superclass for exceptions also gives us the chance to rearrange the exception hierarchy slightly for the better. As it currently stands, all exceptions in the built-in namespace inherit from Exception. This is a problem since this includes two exceptions (KeyboardInterrupt and SystemExit) that often need to be excepted from the application's exception handling: the default behavior of shutting the interpreter down without a traceback is usually more desirable than whatever the application might do (with the possible exception of applications that emulate Python's interactive command loop with ``>>>`` prompt). Changing it so that these two exceptions inherit from the common superclass instead of Exception will make it easy for people to write ``except`` clauses that are not overreaching and not catch exceptions that should propagate up. This PEP is based on previous work done for PEP 348 [#pep348]_. Requiring a Common Superclass ============================= This PEP proposes introducing a new exception named BaseException that is a new-style class and has a single attribute, ``args``. Below is the code as the exception will work in Python 3.0 (how it will work in Python 2.x is covered in the `Transition Plan`_ section):: class BaseException(object): """Superclass representing the base of the exception hierarchy. Provides a 'message' attribute that contains either the single argument to the constructor or the empty string. This attribute is used in the string representation for the exception. This is so that it provides the extra details in the traceback. """ def __init__(self, *args): """Set the 'message' attribute'""" self.args = args def __str__(self): """Return the str of 'message'""" if len(self.args) == 1: return str(self.args[0]) else: return str(self.args) def __repr__(self): return "%s(*%s)" % (self.__class__.__name__, repr(self.args)) No restriction is placed upon what may be passed in for ``args`` for backwards-compatibility reasons. In practice, though, only a single string argument should be used. This keeps the string representation of the exception to be a useful message about the exception that is human-readable; this is why the ``__str__`` method special-cases on length-1 ``args`` value. Including programmatic information (e.g., an error code number) should be stored as a separate attribute in a subclass. The ``raise`` statement will be changed to require that any object passed to it must inherit from BaseException. This will make sure that all exceptions fall within a single hierarchy that is anchored at BaseException [#hierarchy-good]_. This also guarantees a basic interface that is inherited from BaseException. The change to ``raise`` will be enforced starting in Python 3.0 (see the `Transition Plan`_ below). With BaseException being the root of the exception hierarchy, Exception will now inherit from it. Exception Hierarchy Changes =========================== With the exception hierarchy now even more important since it has a basic root, a change to the existing hierarchy is called for. As it stands now, if one wants to catch all exceptions that signal an error *and* do not mean the interpreter should be allowed to exit, you must specify all but two exceptions specifically in an ``except`` clause or catch the two exceptions separately and then re-raise them and have all other exceptions fall through to a bare ``except`` clause:: except (KeyboardInterrupt, SystemExit): raise except: ... That is needlessly explicit. This PEP proposes moving KeyboardInterrupt and SystemExit to inherit directly from BaseException. :: - BaseException |- KeyboardInterrupt |- SystemExit |- Exception |- (all other current built-in exceptions) Doing this makes catching Exception more reasonable. It would catch only exceptions that signify errors. Exceptions that signal that the interpreter should exit will not be caught and thus be allowed to propagate up and allow the interpreter to terminate. KeyboardInterrupt has been moved since users typically expect an application to exit when the press the interrupt key (usually Ctrl-C). If people have overly broad ``except`` clauses the expected behaviour does not occur. SystemExit has been moved for similar reasons. Since the exception is raised when ``sys.exit()`` is called the interpreter should normally be allowed to terminate. Unfortunately overly broad ``except`` clauses can prevent the explicitly requested exit from occurring. To make sure that people catch Exception most of the time, various parts of the documentation and tutorials will need to be updated to strongly suggest that Exception be what programmers want to use. Bare ``except`` clauses or catching BaseException directly should be discouraged based on the fact that KeyboardInterrupt and SystemExit almost always should be allowed to propagate up. Transition Plan =============== Since semantic changes to Python are being proposed, a transition plan is needed. The goal is to end up with the new semantics being used in Python 3.0 while providing a smooth transition for 2.x code. All deprecations mentioned in the plan will lead to the removal of the semantics starting in the version following the initial deprecation. Here is BaseException as implemented in the 2.x series:: class BaseException(object): """Superclass representing the base of the exception hierarchy. The __getitem__ method is provided for backwards-compatibility and will be deprecated at some point. """ def __init__(self, *args): """Set the 'args' attribute.""" self.args = args def __str__(self): """Return the str of args[0] or args, depending on length.""" return str(self.args[0] if len(self.args) <= 1 else self.args) def __repr__(self): func_args = repr(self.args) if self.args else "()" return self.__class__.__name__ + func_args def __getitem__(self, index): """Index into arguments passed in during instantiation. Provided for backwards-compatibility and will be deprecated. """ return self.args[index] Deprecation of features in Python 2.9 is optional. This is because it is not known at this time if Python 2.9 (which is slated to be the last version in the 2.x series) will actively deprecate features that will not be in 3.0 . It is conceivable that no deprecation warnings will be used in 2.9 since there could be such a difference between 2.9 and 3.0 that it would make 2.9 too "noisy" in terms of warnings. Thus the proposed deprecation warnings for Python 2.9 will be revisited when development of that version begins to determine if they are still desired. * Python 2.5 [done] - all standard exceptions become new-style classes - introduce BaseException - Exception, KeyboardInterrupt, and SystemExit inherit from BaseException - deprecate raising string exceptions * Python 2.6 - deprecate catching string exceptions - deprecate ``message`` attribute (see `Retracted Ideas`_) * Python 2.7 - deprecate raising exceptions that do not inherit from BaseException - remove ``message`` attribute * Python 2.8 - deprecate catching exceptions that do not inherit from BaseException * Python 2.9 - deprecate ``__getitem__`` (optional) * Python 3.0 [done] - drop everything that was deprecated above: + string exceptions (both raising and catching) + all exceptions must inherit from BaseException + drop ``__getitem__`` Retracted Ideas =============== A previous version of this PEP that was implemented in Python 2.5 included a 'message' attribute on BaseException. Its purpose was to begin a transition to BaseException accepting only a single argument. This was to tighten the interface and to force people to use attributes in subclasses to carry arbitrary information with an exception instead of cramming it all into ``args``. Unfortunately, while implementing the removal of the ``args`` attribute in Python 3.0 at the PyCon 2007 sprint [#pycon2007-sprint-email]_, it was discovered that the transition was very painful, especially for C extension modules. It was decided that it would be better to deprecate the ``message`` attribute in Python 2.6 (and remove in Python 2.7 and Python 3.0) and consider a more long-term transition strategy in Python 3.0 to remove multiple-argument support in BaseException in preference of accepting only a single argument. Thus the introduction of ``message`` and the original deprecation of ``args`` has been retracted. References ========== .. [#pep348] PEP 348 (Exception Reorganization for Python 3.0) http://www.python.org/peps/pep-0348.html .. [#hierarchy-good] python-dev Summary for 2004-08-01 through 2004-08-15 http://www.python.org/dev/summary/2004-08-01_2004-08-15.html#an-exception-i… .. [#SF_1104669] SF patch #1104669 (new-style exceptions) http://www.python.org/sf/1104669 .. [#pycon2007-sprint-email] python-3000 email ("How far to go with cleaning up exceptions") http://mail.python.org/pipermail/python-3000/2007-March/005911.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:

3 3

Re: [Python-Dev] Integrate BeautifulSoup into stdlib?
by Jim Jewett 05 Apr '09

05 Apr '09

Michael Foord wrote: > Chris Withers wrote: >> ... love to see ... but ... not optimistic >> - python to grow a decent, cross platform, package management system As stated, this may be impossible, because of the difference in what a package should mean on Windows vs Unix. If you just mean a way to add python packages from pypi as with EasyInstall, then maybe. >> - the standard library to actually shrink to a point where only >> libraries that are not released elsewhere are included In some environments, each new component must be approved. Once python is approved, the standard library is OK, but adding 7 packages from pypi requires 7 more sets of approvals. On the other hand, if there were a way to say "The PSF explicitly endorses Packages X, Y, and Z as worthy of the stdlib; they are distributed separately for administrative reasons", then the initial request could be for "Python plus officially endorsed addons" That said, it may make sense to just give greater prominence to existing repackagers, such as ActiveState or Enthought. > If a library is well maintained then there seems to be little point in > moving it into the standard library The official endorsement is in many cases more important than shared distribution. -jJ

37 134

Re: [Python-Dev] [Distutils] unicode bug in distutils
by Phillip J. Eby 05 Apr '09

05 Apr '09

At 02:47 PM 2/24/2007 -0600, Tarek Ziadé wrote: >I have created a setup.py file for distirbution and I bumped into >a small bug when i tried to set my name in the contact field (Tarek Ziadé) > >Using string (utf8 file): > >setup( > maintainer="Tarek Ziadé" >) > >leads to: > > File ".../lib/python2.5/distutils/command/register.py", line 162, in > send_metadata > auth) > File ".../lib/python2.5/distutils/command/register.py", line 257, in > post_to_server > value = unicode(value).encode("utf-8") >UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 10: >ordinal not in range(128) > > >Using unicode: > >setup( > maintainer=u"Tarek Ziadé" >) > >leads to: > > File ".../lib/python2.5/distutils/dist.py", line 1094, in write_pkg_file > file.write('Author: %s\n' % self.get_contact() ) >UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in >position 18: ordinal not in range(128) > >I would propose a patch for this problem but i don't know what would be >the best input (i guess unicode > for names) At 05:45 PM 2/24/2007 -0500, Tres Seaver wrote: >Don't you still need to tell Python about the encoding of your string >literals [1] [2] ? E.g.:: That's not the problem, it's that the code that writes the PKG-INFO file doesn't handle Unicode. See distutils.dist.DistributionMetadata.write_pkg_info(). It needs to use a file with encoding support, if it's doing unicode However, there's currently no standard, as far as I know, for what encoding the PKG-INFO file should use. Meanwhile, the 'register' command accepts Unicode, but is broken in handling it. Essentially, the problem is that Python 2.5 broke this by adding a unicode *requirement* to the "register" command. Previously, register simply sent whatever you gave it, and the PKG-INFO writing code still does. Unfortunately, this means that there is no longer any one value that you can use for your name that will be accepted by both "register" and anything that writes a PKG-INFO file. Both register and write_pkg_info() are arguably broken here, and should be able to work with either strings or unicode, and degrade gracefully in the event of non-ASCII characters in a string. (Because even though "register" is only run by the package's author, users may run other commands that require a PKG-INFO, so a package prepared using Python <2.5 must still be usable with Python 2.5 distutils, and Python <2.5 allows 8-bit maintainer names.) Unfortunately, this isn't fixable until there's a new 2.5.x release. For previous Python versions, both register and write_pkg_info() accepted 8-bit strings and passed them on as-is, so the only workaround for this issue at the moment is to revert to Python 2.4 or less.

4 5

Re: [Python-Dev] And the winner is...
by Mike Coleman 04 Apr '09

04 Apr '09

Just for curiosity's sake, could someone outline the five (or so) most significant pluses of hg relative to git? (My personal feeling is that any of the three is a huge improvement over subversion. I think git probably should have been written in Python with some stuff in C where necessary, and (perhaps) the hg guy really is right when he claims that Linus should have skipped git and used hg from the start. That notwithstanding, though, it kind of looks like git has won the mindshare war at this point, and I think the best hg can hope for from this point forward is a sort of *BSD to git's Linux. I do hope that it lives on, shutouts being fascist, etc. Aside: I once worked with the guy maintaining git, and he might have the greatest sum of talent plus humility of any programmer I ever met.)

13 19

Let's update CObject API so it is safe and regular!
by Larry Hastings 03 Apr '09

03 Apr '09

The CObject API has two flaws. First, there is no usable type safety mechanism. You can store a void *object, and a void *description. There is no established schema for the description; it could be an integer cast to a pointer, or it could point to memory of any configuration, or it could be NULL. Thus users of the CObject API generally ignore it--thus working without any type safety whatsoever. A programmer could crash the interpreter from pure Python by mixing and matching CObjects from different modules (e.g. give "curses" a CObject from "_ctypes"). Second, the destructor callback is defined as taking *either* one *or* two parameters, depending on whether the "descr" pointer is non-NULL. One can debate the finer points of what is and isn't defined behavior in C, but at its heart this is a sloppy API. MvL and I discussed this last night and decided to float a revision of the API. I wrote the patch, though, so don't blame Martin if you don't like my specific approach. The color of this particular bike shed is: * The PyCObject is now a private data structure; you must use accessors. I added accessors for all the members. * The constructors and the main accessor (PyCObject_AsVoidPtr) now all *require* a "const char *type" parameter, which must be a non-NULL C string of non-zero length. If you call that accessor and the "type" is invalid *or doesn't match*, it fails. * The destructor now takes the PyObject *, not the PyCObject *. You must use accessors to get your hands on the data inside to free it. Yes, you can easily skip around the "matching type" restriction by calling PyCObject_AsVoidPtr(cobj, PyCObject_GetType(cobj)). The point of my API changes is to *encourage* correct use. I've posted a patch implementing this change in the 3.1 trunk to the bug tracker: http://bugs.python.org/issue5630 I look forward to your comments! /larry/

8 24

3to2 Project
by Jesse Noller 03 Apr '09

03 Apr '09

During the Language summit this past Thursday, pretty much everyone agreed that a python 3 to python 2 tool would be a very large improvement in helping developers be able to write "pure" python 3 code. The idea being a large project such as Django could completely cut over to Python3, but then run the 3to2 tool on the code based to continue to support version 2.x. I raised my hand to help move this along, I've spoke to Benjamin Peterson, and he's amendable to mentoring a GSoC student for this project and he's already received at least one proposal for this. Additionally, there's been a number of developers here at PyCon who are more than ready to help contribute. So, if people are interested in helping, coordinating work/etc - feel free to sync up with Benjamin - he's started a wiki page here: http://wiki.python.org/moin/3to2 I'll help coordinate where I can! -Jesse

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3.1a2
by Benjamin Peterson 02 Apr '09

02 Apr '09

Hi, I'd like to release the second alpha of 3.1 as planned on Saturday, April 4th. There are currently two release blockers, issues #4847 and #5470. #5470 appears to be Martin's issue. I haven't looked at #4847 in depth, but appears that the csv module will need some API changes to deal with encodings. Perhaps somebody would like to sprint on it? -- Regards, Benjamin

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splitting out bdist_* (was: interminable 'setuptools' thread)
by glyph＠divmod.com 02 Apr '09

02 Apr '09

On 07:59 pm, fdrake(a)acm.org wrote: >I'm actually in favor of removing the bdist_* from the standard >library, and allowing 3rd-party tools to implement whatever they need >for the distros. But I don't think what you're presenting there >supports it. I do think that it's relevant that the respective operating system packagers don't find bdist_rpm, bdist_deb, et. al. useful. It's not very useful to have a bdist_deb that nobody actually builds debs with. This has been a problem for me, personally, since debian has made various ad-hoc change to Twisted or Twisted-based packages to break our plugin system, since the distutils metadata has been insufficient for their purposes. If the deb-generating stuff were in a separate project with a faster release cycle that were easier to contribute packages to, perhaps debian packagers could be convinced to contribute their build- hacks there (and bdist_deb could invoke debhelper, or vice-versa). It would be great if someone could volunteer to maintain this stuff independently, put it in a Launchpad project or something. IMHO it would be better for the community at large if this were spun as "increasing the release speed" of the bdist_* family, rather than "removing", which seems to me like it would generate another teacup- tempest on the blogowebs. Of course I'm not volunteering, but I will be best friends forever with whoever does this PR/maintenance :). Given that py2exe and py2app (which includes "bdist_mpkg") are both based on distutils, it seems like we're on the way to independent maintenance anyway. Perhaps bdist_wininst/_msi could be donated to the py2exe project if they would be willing to maintain it, and the new project for _deb and _rpm could be called "py2packman" or something.

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Re: [Python-Dev] Broken import?
by Guido van Rossum 01 Apr '09

01 Apr '09

[Adding python-dev. I'm quoting the entire original message.] > On Thu, Mar 19, 2009 at 6:40 PM, Fredrik Lundh <fredriklundh(a)google.com> wrote: >> PS. Is it just me, or is import broken in 3.0? Consider this: >> >> $ more package\a.py >> print("in a") >> >> import b >> >> def a(): >> print("here") >> >> def main(): >> b.b() >> >> $ more package\b.py >> print("in b") >> >> import a >> >> def b(): >> a.a() >> >> Under 2.X, this prints "in a" "in b" and "here", as expected. Under >> 3.0, using the "from . import" form for relative imports, it bombs out >> with a: >> >> in a >> in b >> Traceback (most recent call last): >> File "main.py", line 1, in <module> >> from package import a >> File "package/a.py", line 3, in <module> >> from . import b >> File "package\b.py", line 3, in <module> >> from . import a >> ImportError: cannot import name a >> >> Sure, it's a recursive import, but there's no recursive dependency >> here - nobody will access the module contents until the main program >> calls the library. What am I missing? On Mon, Mar 30, 2009 at 5:44 PM, Guido van Rossum <guido(a)python.org> wrote: > I reproduced this, but it seems to have more to do with "from . import > ..." than with the Python version. If I add the "from ." before each > of the imports, "python -c 'import p.a' " fails with roughly the above > traceback for any version of Python that supports this syntax, while > without that it passes for any 2.x. > > If I use the "from ." syntax in a.py but not in b.py, "import p.a" > passes but "import p.b" fails. > > I'll see if anyone present at the sprints has a clue. Made some progress. Anything using "from <whatever> import b" (where <whatever> is either '.' or 'p') will fail when b's import is not completed. OTOH using "import p.b" works. I reduced it to: p/a.py == "from p import b" p/b.py == "import a" python -c "import p.b" The reason seems to be that until the outermost import (in this case p.b) is completed, while sys.modules has the (incomplete) modules 'p', 'p.a' and 'p.b', the attributes p.a and p.b aren't added until after their import is completed. Which it isn't during recursive import. Apparently 'from <anything> import <something>' looks for the <something> attribute in the <parent> object. This is because "from...import" can also be used to import objects other than modules (e.g. "from M import C"). I'm guessing that setting the attribute is delayed until the import is totally complete, because upon a failed import we remove the half-imported module object from sys.modules, but apparently we didn 't want to be in the business of removing the attribute from the parent package, so that's only set after the import is deemed successful. At least, this is my hypothesis, thinking about it -- I might look at the code later. :-) The most portable solution is to avoid "from...import" and instead write something like import p.b as b -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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Test failures under Windows?
by Antoine Pitrou 01 Apr '09

01 Apr '09

Hello, I've just tried running test_io under Windows (in a virtual machine) and I get the following failures: ====================================================================== ERROR: test_error_through_destructor (test.test_io.CTextIOWrapperTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "Z:\py3k\__svn__\lib\test\test_io.py", line 1543, in test_error_through_d estructor self.assertRaises(AttributeError, f) File "Z:\py3k\__svn__\lib\unittest.py", line 457, in failUnlessRaises callableObj(*args, **kwargs) File "Z:\py3k\__svn__\lib\test\test_io.py", line 1541, in f self.TextIOWrapper(rawio).xyzzy OSError: [Errno 9] Bad file descriptor ====================================================================== ERROR: test_error_through_destructor (test.test_io.PyTextIOWrapperTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "Z:\py3k\__svn__\lib\test\test_io.py", line 1543, in test_error_through_d estructor self.assertRaises(AttributeError, f) File "Z:\py3k\__svn__\lib\unittest.py", line 457, in failUnlessRaises callableObj(*args, **kwargs) File "Z:\py3k\__svn__\lib\test\test_io.py", line 1541, in f self.TextIOWrapper(rawio).xyzzy File "Z:\py3k\__svn__\lib\_pyio.py", line 1356, in __init__ encoding = os.device_encoding(buffer.fileno()) OSError: [Errno 9] Bad file descriptor ---------------------------------------------------------------------- Am I the only one getting those? By the way, what happened to the Windows buildbots? Regards Antoine.

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Re: [Python-Dev] This seems like a bug - main thread has None ident???
by skip＠pobox.com 01 Apr '09

01 Apr '09

skip> Am I missing something obvious or have I hit a bug? This is a skip> fully updated 2.7a0 build, trunk:70878M. After noting that thread.get_ident() returned a thread id but that threading.currentThread().ident was None I concluded that it is, in fact, a bug in the threading module. I opened a ticket: http://bugs.python.org/issue5632 Skip

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This seems like a bug - main thread has None ident???
by skip＠pobox.com 01 Apr '09

01 Apr '09

Looking for some quick feedback on this. I've bumped into what looks like a bug in the threading module. From the interpreter prompt: >>> import threading >>> threading.currentThread() <_MainThread(MainThread, started)> >>> print threading.currentThread().ident None The ident attribute is documented as being a number unless the thread has yet to be started. Shouldn't the main thread's ident attribute *always* be non-None? Clearly, it appears the main thread has been started. Am I missing something obvious or have I hit a bug? This is a fully updated 2.7a0 build, trunk:70878M. Skip

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regrtest behavior change
by R. David Murray 01 Apr '09

01 Apr '09

At the sprint the developers decided that a long standing issue with regrtest should be fixed: the fact that invalid imports in tests can result in a test being skipped instead of producing an error. I've just checked in a change to regrtest on the trunk. It no longer assumes that an ImportError means the test should be marked as skipped. I have done my best to wrap all imports where errors _should_ cause skips in the appropriate wrappers from test_support (import_module or get_attribute). Of course, since I can't run the tests on all possible systems I may have missed some. It's also possible that making this change will unmask some errors that have been hidden by the previous behavior, although I haven't found any instances of that so far. Another issue is that there may be modules that don't exist on other VM implementations where those modules would have been skipped on a test run previous to this, and will now generate an ImportError. We will happily wrap imports for those modules when informed that such should be done. I'll be watching the buildbots, but please let me know about any issues that you find. I'll be merging it to py3k as well, but there will be no backport. -- R. David Murray http://www.bitdance.com

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And the winner is...
by Guido van Rossum 01 Apr '09

01 Apr '09

Dear Python developers, The decision is made! I've selected a DVCS to use for Python. We're switching to Mercurial (Hg). The implementation and schedule is still up in the air -- I am hoping that we can switch before the summer. It's hard to explain my reasons for choosing -- like most language decisions (especially the difficult ones) it's mostly a matter of gut feelings. One thing I know is that it's better to decide now than to spend another year discussing the pros and cons. All that could be said has been said, pretty much, and my mind is made up. To me, the advantages of using *some* DVCS are obvious. At PyCon, Brett already announced that Git was no longer being considered -- while it has obviously many fans, it also provokes strong antipathies. So it was between Hg and Bzr (both of which happen to be implemented in Python FWIW). Based on a completely unscientific poll (basically whatever feedback I received in my personal inbox or on Twitter), Hg has a strong following among Python developers and few detractors, while few (except Canonical employees) seem to like Bzr. In addition, most timing experiments point towards Hg being faster than Bzr for most operations, and Hg is (again, subjectively) easier to learn for SVN users than Bzr. -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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Re: [Python-Dev] [Python-ideas] CapPython's use of unbound methods
by Guido van Rossum 31 Mar '09

31 Mar '09

[Adding back python-dev, I don't want this discussion fragmented.] Denis, I am arguing with Mark because he and others claim that it is possible to add capabilities to Python *without* changing the flavor of the language (much), and because he believes that using a subset of Python is somehow helpful for Python programmers (or helps Python programmers transitioning to CapPython). I'm trying to point out the limitations of that approach. In the past capability zealots have also requested forcefully that Python should support capabilities natively. This sounds like an unrealistic evolutionary path for the language, and I'm pointing that out. (Certainly I don't see CapPython as a step in that direction -- perhaps Tav's approach could be.) If they are happy with a different language that happens to resemble Python is some syntactic details that would be fine of course, but then they shouldn't whine that Py3k breaks their implementation. I also suspect that Mark's approach might be easily crackable because he doesn't know the CPython implementation well enough to be aware of all possible attack vectors. --Guido On Tue, Mar 31, 2009 at 4:22 AM, spir <denis.spir(a)free.fr> wrote: > Le Mon, 30 Mar 2009 16:19:51 -0500, > Guido van Rossum <guido(a)python.org> s'exprima ainsi: > > [...] >> > Fortunately CapPython does not have to make this kind of semantic >> > change. >> >> Well of course it makes a much more severe semantic change by >> declaring illegal all use of attribute names starting with underscore. > [...] > > Hello, > > I wonder what's the meaning of this exchange. As I understand it, the point of CapPython is precisely to build a different dialect which semantic field is restricted, in order to comply with the so-called "Object-Capability" security guidelines. > We may like it or not. So what? I won't use CapPython, but I'm pleased to see people do language experiments on a Python basis. > Now, I also understand this: if ever for you CapPython breaks fondamental design choices, then you may not like, as Python inventor, this projects to be called *Python. I would even agree, from a moral point of view, with a demand for a name change. > > (Sorry if this sounds a bit rude. Not sure of idiom connotations in english. I prefere clarity to hypocrisy.) > > Denis > > PS: I had a kind of ProtoPython in mind. If ever someone comments that it's a major semantic change; that it does not let pythonistas use their beloved class-ic idioms; then I'll just laugh... Yes, it's even a major cognitive change. This is precisely the intent. So what? > > ------ > la vita e estrany > -- --Guido van Rossum (home page: http://www.python.org/~guido/)

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CMake Evaluation
by Bill Hoffman 31 Mar '09

31 Mar '09

Hi, I noticed the thread on CMake evaluation, and as a CMake developer I am interested in helping you evaluate CMake. I guess four issues were raised: >A. It has no equivalent of autoheader, so we'd have to maintain pyconfig.h.in by hand. This is currently true, but if this were a deal breaker, I am sure something could be added to CMake to accommodate the need. It might even be possible to create a CMake function that does something like this without having to modify CMake itself. >B. It does not allow the CMakeLists.txt file control the --help output. This appears to be an intentional decision (http://www.cmake.org/pipermail/cmake-promote/2006-May/000095.html). To replace it, they have an interactive mode (which asks you about each possible option) and a -LH flag (which runs the whole configure process and then tells you about the flags you could have set if you knew about them). CMake now has a cmake-gui (qt based application) for configuring a project. C. It does not allow the CMakeLists.txt file to see the command line, so we can't stay backward compatible with the configure script, and we'd have to replace flags like --with-pydebug with -Dpydebug:bool=true. We could write a separate configure script to mitigate this and the previous problem, but we'd have to keep that in sync with CMakeLists.txt manually. We have talked about adding this to CMake several times, and it is a good idea. However, it has not been a huge issue for many projects. D. It doesn't have an expression language, so to replace ac_md_system=`echo $ac_sys_system | tr -d '[/ ]' | tr '[[A-Z]]' '[[a-z]]'` you have to write: string(REGEX REPLACE "[/ ]" "" ac_md_system ${ac_sys_system}) string(TOLOWER ${ac_md_system} ac_md_system) However, the above CMake script will work on any platform with CMake installed, and does not use tr. Also, the CMake code for the above should actually run faster as it is not running two processes with pipe communication. I would not think that this list of issues would be a deal breaker. The benefits of CMake are a single build system that works cross platform. Developers can use the native tools that they are used to using (VS IDE, Xcode IDE, Eclipse IDE, nmake command line, gmake command line, etc.). The original Python CMake work done by Alex, was done to support the building of ParaView (www.paraview.org) on a Cray Xt5 computer using CMake's cross-compilation support. This worked very well. The choice is obviously yours to make, but if you have any specific questions about CMake, I will lurk on this mailing list and try to answer them. I think it would be a good fit for CMake to build Python, and make things easier for some of our customers building ParaView which depends on Python on machines like the Cray Xt5. Thanks. -Bill

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