Python-Dev February 2005

python-dev@python.org

94 participants
99 discussions

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

Re: subprocess and EINTR errnos
by Peter Astrand 06 Jul '09

06 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

Memory Allocator Part 2: Did I get it right?
by Evan Jones 11 Mar '05

11 Mar '05

After I finally understood what thread-safety guarantees the Python memory allocator needs to provide, I went and did some hard thinking about the code this afternoon. I believe that my modifications provide the same guarantees that the original version did. I do need to declare the arenas array to be volatile, and leak the array when resizing it. Please correct me if I am wrong, but the situation that needs to be supported is this: While one thread holds the GIL, any other thread can call PyObject_Free with a pointer that was returned by the system malloc. The following situation is *not* supported: While one thread holds the GIL, another thread calls PyObject_Free with a pointer that was returned by PyObject_Malloc. I'm hoping that I got things a little better this time around. I've submitted my updated patch to the patch tracker. For reference, I've included links to SourceForge and the previous thread. Thank you, Evan Jones Previous thread: http://mail.python.org/pipermail/python-dev/2005-January/051255.html Patch location: http://sourceforge.net/tracker/index.php? func=detail&aid=1123430&group_id=5470&atid=305470

4 8

unicode inconsistency?
by Neil Schemenauer 09 Mar '05

09 Mar '05

Perhaps this is more approprate for python-list but I looks like a bug to me. Example code: class A: def __str__(self): return u'\u1234' '%s' % u'\u1234' # this works '%s' % A() # this doesn't work It will work if 'A' subclasses from 'unicode' but should not be necessary, IMHO. Any reason why this shouldn't be fixed? Neil

6 15

Requesting that a class be a new-style class
by Nick Coghlan 05 Mar '05

05 Mar '05

This is something I've typed way too many times: Py> class C(): File "<stdin>", line 1 class C(): ^ SyntaxError: invalid syntax It's the asymmetry with functions that gets to me - defining a function with no arguments still requires parentheses in the definition statement, but defining a class with no bases requires the parentheses to be omitted. Which leads in to the real question: Does this *really* need to be a syntax error? Or could it be used as an easier way to spell "class C(object):"? Then, in Python 3K, simply drop support for omitting the parentheses from class definitions - require inheriting from ClassicClass instead. This would also have the benefit that the elimination of defaulting to classic classes would cause a syntax error rather than subtle changes in behaviour. Cheers, Nick. -- Nick Coghlan | ncoghlan(a)email.com | Brisbane, Australia --------------------------------------------------------------- http://boredomandlaziness.skystorm.net

9 13

a bunch of Patch reviews
by Irmen de Jong 03 Mar '05

03 Mar '05

Hello I've looked at one bug and a bunch of patches and added a comment to them: (bug) [ 1102649 ] pickle files should be opened in binary mode Added a comment about a possible different solution [ 946207 ] Non-blocking Socket Server Useless, what are the mixins for? Recommend close [ 756021 ] Allow socket.inet_aton('255.255.255.255') on Windows Looks good but added suggestion about when to test for special case [ 740827 ] add urldecode() method to urllib I think it's better to group these things into urlparse [ 579435 ] Shadow Password Support Module Would be nice to have, I recently just couldn't do the user authentication that I wanted: based on the users' unix passwords [ 1093468 ] socket leak in SocketServer Trivial and looks harmless, but don't the sockets get garbage collected once the request is done? [ 1049151 ] adding bool support to xdrlib.py Simple patch and 2.4 is out now, so... It would be nice if somebody could have a look at my own patches or help me a bit with them: [ 1102879 ] Fix for 926423: socket timeouts + Ctrl-C don't play nice [ 1103213 ] Adding the missing socket.recvall() method [ 1103350 ] send/recv SEGMENT_SIZE should be used more in socketmodule [ 1062014 ] fix for 764437 AF_UNIX socket special linux socket names [ 1062060 ] fix for 1016880 urllib.urlretrieve silently truncates dwnld Some of them come from the last Python Bug Day, see http://www.python.org/moin/PythonBugDayStatus Thank you ! Regards, --Irmen de Jong

6 18

Patch Reviewing
by Reinhold Birkenfeld 03 Mar '05

03 Mar '05

Hello, just felt a little bored and tried to review a few (no-brainer) patches. Here are the results: * Patch #1051395 Minor fix in Lib/locale.py: Docs say that function _parse_localename returns a tuple; but for one codepath it returns a list. Patch fixes this by adding tuple(), recommending apply. * Patch #1046831 Minor fix in Lib/distutils/sysconfig.py: it defines a function to retrieve the Python version but does not use it everywhere; Patch fixes this, recommending apply. * Patch #751031 Adds recognizing JPEG-EXIF files (produced by digicams) to imghdr.py. Recommending apply. * Patch #712317 Fixes URL parsing in urlparse for URLs such as http://foo?bar. Splits at '?', so assigns 'foo' to netloc and 'bar' to query instead of assigning 'foo?bar' to netloc. Recommending apply. regards, Reinhold

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Re: [Python Dev] PEP 309
by Peter Harris 01 Mar '05

01 Mar '05

>>Overall, I have no major objections to the PEP or the patch. Before it >>goes in on auto-pilot, it would be darned nice if the proponents said >>that they've found it helpful in real code and that they are satisfied >>with the timings. >> >> > >I guess "darned nice" is the best you can hope for. Not sure if Peter >Harris is still around. > >Regards, >Martin > > Yes, I'm still lurking, slightly aghast that my little PEP is getting such ferocious scrutiny. I would have like some of that in time for it to go into 2.4, but I suppose you should be careful what you wish for. I'll answer a few points from this thread, in no particular order: My original desire was a built-in, but it was suggested that the first step would be a Python implementation in the standard library to try it out. That was the basis for the PEP, and in fact a C implementation would have been beyond my expertise. However, I sympathise with anyone who feels unhappy about a new module just for what amounts to one function. I'd be happy to go back to the built-in, now someone cleverer than I am has written one. Sorry I can't rememeber your name, whoever you are. I'm having trouble with my e-mails. I was never too bothered about efficiency, and still am not. For me it was always primarily a way to save typing or build call-back functions on the fly. The discussion about using it to make instancemethods and classmethods -- way over my head! I would count that as something weird enough to be worth spelling out in "plain Python", in my code anyway. The PEP was scattered over a few patches because I wasn't too sure how to go about it, so there was my Python module, the C implementation, the unit tests and the docs all in separate patches. 3/4 of that was my fault - sorry! Once the PEP had been accepted, I didn't like to mess with it, which is why I went quiet for a while. It's gone past the point where I can personally contribute much, so I'd just like to say thanks and I look forward to the day when I can just use it. Peter Harris

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RE: [Python-Dev] Re: PEP 754
by Warnes, Gregory R 28 Feb '05

28 Feb '05

[After a long delay, the thread continues....] Hi All, I'm pushing ahead on the tasks necessary to add the 'fcponst' module described in PEP 754: IEEE 754 Floating Point Special Values. Per http://www.python.org/psf/contrib, I've - Changed the license to the Apache License, Version 2.0 - Just faxed the "Contributor Agreement" to the PSF I've also - created a patch on sourceforge.net for fpconst code and documentation (see https://sourceforge.net/tracker/index.php?func=detail&aid=1151323&group_id=5 470&atid=305470) I will need help connecting the included test functions into the python test suite. What else needs to be done to allow fpconst to go into the Python library? -Greg > -----Original Message----- > From: Tim Peters [mailto:tim.one@comcast.net] > Sent: Friday, December 10, 2004 1:43 PM > To: Warnes, Gregory R; goodger(a)python.org > Cc: peps(a)python.org > Subject: RE: [Python-Dev] Re: PEP 754 > > > [Warnes, Gregory R] > > Hi David & Tim, > > > > First, I really like to see this go forward. The fpconst module is > > getting alot of use across the net, and it would be very useful to > > finally get it into the standard python library. What > needs to be done > > to move forward? > > Looks to me like exactly the same stuff as was needed before. > Guido needs > to pronounce on it. It needs a patch on SourceForge, adding > the new module, > new docs, and a test suite run by Python's standard regrtest.py. The > non-PSF copyright and license remain problematic. That last should be > easier to deal with after the PSF approves a Contributor > Agreement (probably > within a month), but will be a show-stopper if Pfizer won't > contribute the > module under the terms of the Contributor Agreement (which > can't be answered > now by anyone, since the Contributor Agreement doesn't exist yet). > > > LEGAL NOTICE Unless expressly stated otherwise, this message is confidential and may be privileged. It is intended for the addressee(s) only. Access to this E-mail by anyone else is unauthorized. If you are not an addressee, any disclosure or copying of the contents of this E-mail or any action taken (or not taken) in reliance on it is unauthorized and may be unlawful. If you are not an addressee, please inform the sender immediately.

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PEP 309 enhancements
by Nick Coghlan 28 Feb '05

28 Feb '05

Moving a discussion from the PEP309 SF tracker (Patch #941881) to here, since it's gone beyond the initial PEP 309 concept (and the SF tracker is a lousy place to have a design discussion, anyway). The discussion started when Steven Bethard pointed out that partial objects can't be used as instance methods (using new.instancemethod means that the automatically supplied 'self' argument ends up in the wrong place, after the originally supplied arguments). This problem is mentioned only indirectly in the PEP (pointing out that a version which prepended later arguments, rather than appending them might be useful). Such a class wouldn't solve the problem anyway, as it is only the *first* argument we want to give special treatment. Keyword arguments won't help us, since the 'self' argument is always positional. The initial suggestion was to provide a __get__ method on partial objects, which forces the insertion of the reference to self at the beginning of the argument list instead of at the end: def __get__(self, obj, type=None): if obj is None: return self return partial(self.fn, obj, *self.args, **self.kw) However, this breaks down for nested partial functions - the call to the nested partial again moves the 'self' argument to after the originally supplied argument list. This can be addressed by automatically 'unfolding' nested partials (which should also give a speed benefit when supplying arguments piecemeal, since building incrementally or all at once will get you to the same place): def __init__(*args, **kw): self = args[0] try: func = args[1] except IndexError: raise TypeError("Expected at least 2 arguments, got %s" % len(args)) if isinstance(func, partial): self.fn = func.fn self.args = func.args + args[2:] d = func.kw.copy() d.update(kw) self.kw = d else: self.fn, self.args, self.kw = (func, args[2:], kw) At this point, the one thing you can't do is use a partial function as a *class* method, as the classmethod implementation doesn't give descriptors any special treatment. So, instead of the above, I propose the inclusion of a callable 'partialmethod' descriptor in the functional module that takes the first positional argument supplied at call time and prepends it in the actual function call (this still requires automatic 'unfolding'in order to work correctly with nested partial functions): class partialmethod(partial): def __call__(self, *args, **kw): if kw and self.kw: d = self.kw.copy() d.update(kw) else: d = kw or self.kw if args: first = args[:1] rest = args[1:] else: first = rest = () return self.fn(*(first + self.args + rest), **d) def __get__(self, obj, type=None): if obj is None: return self return partial(self.fn, obj, *self.args, **self.kw) Using a function that simply prints its arguments: Py> class C: ... a = functional.partialmethod(f, 'a') ... b = classmethod(functional.partialmethod(f, 'b')) ... c = staticmethod(functional.partial(f, 'c')) ... d = functional.partial(functional.partialmethod(f, 'd', 1), 2) ... Py> C.e = new.instancemethod(functional.partialmethod(f, 'e'), None, C) Py> C().a(0) ((<__main__.C instance at 0x00A95710>, 'a'), {}, 0) Py> C().b(0) (<class __main__.C at 0x00A93FC0>, 'b', 0) Py> C().c(0) ('c', 0) Py> C().d(0) ('d', 1, 2, 0) Py> C().e(0) (<__main__.C instance at 0x00A95710>, 'e', 0) Notice that you *don't* want to use partialmethod when creating a static method. Cheers, Nick. -- Nick Coghlan | ncoghlan(a)email.com | Brisbane, Australia --------------------------------------------------------------- http://boredomandlaziness.skystorm.net

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Python-Dev February 2005