Python-Dev June 2008

python-dev@python.org

122 participants
123 discussions

by Rotem Yaari

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

10 years, 9 months

Re: subprocess and EINTR errnos

by Peter Astrand

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>

11 years

deprecating BaseException.message

by Brett Cannon

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:

11 years, 3 months

Re: [Python-Dev] [Distutils] unicode bug in distutils

by Phillip J. Eby

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.

11 years, 3 months

Python + Java Integration

by Chas Emerick

This may seem like it's coming out of left field for a minute, but bear with me. There is no doubt that Ruby's success is a concern for anyone who sees it as diminishing Python's status. One of the reasons for Ruby's success is certainly the notion (originally advocated by Bruce Tate, if I'm not mistaken) that it is the "next Java" -- the language and environment that mainstream Java developers are, or will, look to as a natural next step. One thing that would help Python in this "debate" (or, perhaps simply put it in the running, at least as a "next Java" candidate) would be if Python had an easier migration path for Java developers that currently rely upon various third-party libraries. The wealth of third-party libraries available for Java has always been one of its great strengths. Ergo, if Python had an easy-to-use, recommended way to use those libraries within the Python environment, that would be a significant advantage to present to Java developers and those who would choose Ruby over Java. Platform compatibility is always a huge motivator for those looking to migrate or upgrade. In that vein, I would point to JPype (http://jpype.sourceforge.net). JPype is a module that gives "python programs full access to java class libraries". My suggestion would be to either: (a) include JPype in the standard library, or barring that, (b) make a very strong push to support JPype (a) might be difficult or cumbersome technically, as JPype does need to build against Java headers, which may or may not be possible given the way that Python is distributed, etc. However, (b) is very feasible. I can't really say what "supporting JPype" means exactly -- maybe GvR and/or other heavyweights in the Python community make public statements regarding its existence and functionality, maybe JPype gets a strong mention or placement on python.org....all those details are obviously not up to me, and I don't know the workings of the "official" Python organizations enough to make serious suggestions. Regardless of the form of support, I think raising people's awareness of JPype and what it adds to the Python environment would be a Good Thing (tm). For our part, we've used JPype to make PDFTextStream (our previously Java-only PDF text extraction library) available and supported for Python. You can read some about it here: http://snowtide.com/PDFTextStream.Python And I've blogged about how PDFTextStream.Python came about, and how we worked with Steve Ménard, the maintainer of JPype, to make it all happen (watch out for this URL wrapping): http://blog.snowtide.com/2006/08/21/working-together-pythonjava-open- sourcecommercial Cheers, Chas Emerick Founder, Snowtide Informatics Systems Enterprise-class PDF content extraction cemerick(a)snowtide.com http://snowtide.com | +1 413.519.6365

11 years, 7 months

Proposal: add odict to collections

by Armin Ronacher

Hi, I noticed lately that quite a few projects are implementing their own subclasses of `dict` that retain the order of the key/value pairs. However half of the implementations I came across are not implementing the whole dict interface which leads to weird bugs, also the performance of a Python implementation is not that great. To fight that problem I want to proposed a new class in "collections" called odict which is a dict that keeps the items sorted, similar to a PHP array. The interface would be fully compatible with dict and implemented as dict subclass. Updates to existing keys does not change the order of a key but new keys are inserted at the end. Additionally it would support slicing where a list of key, value tuples is returned and sort/reverse/index methods that work like their list equivalents. Index based lookup could work via odict.byindex(). An implementation of that exists as part of the ordereddict implementation which however goes beyond that and is pretty much a fork of the python dict[1]. Some reasons why ordered dicts are a useful feature: - in XML/HTML processing it's often desired to keep the attributes of an tag ordered during processing. So that input ordering is the same as the output ordering. - Form data transmitted via HTTP is usually ordered by the position of the input/textarea/select field in the HTML document. That information is currently lost in most Python web applications / frameworks. - Eaiser transition of code from Ruby/PHP which have sorted associative arrays / hashmaps. - Having an ordered dict in the standard library would allow other libraries support them. For example a PHP serializer could return odicts rather then dicts which drops the ordering information. XML libraries such as etree could add support for it when creating elements or return attribute dicts. Regards, Armin [1]: http://www.xs4all.nl/~anthon/Python/ordereddict/

11 years, 10 months

optimization required: .format() is much slower than %

by Christian Heimes

Dear fellow Python developers! Ten minutes ago I raised a concern about speed differences between the old style % formatting and the new .format() code. Some quick benchmarking from Benjamin and me showed, that it's even worse than I expected. $ ./python -m timeit "'%s'.format('nothing')" 100000 loops, best of 3: 2.63 usec per loop $ ./python -m timeit "'%s' % 'nothing'" 10000000 loops, best of 3: 0.188 usec per loop $ ./python -m timeit "'some text with {0}'.format('nothing')" 100000 loops, best of 3: 4.34 usec per loop $ ./python -m timeit "'some text with %s' % 'nothing'" 100000 loops, best of 3: 2.04 usec per loop $ ./python -m timeit "'some text with {0} {1}'.format('nothing', 'more')" 100000 loops, best of 3: 6.77 usec per loop $ ./python -m timeit "'some text with %s %s' % ('nothing', 'more')" 100000 loops, best of 3: 2.22 usec per loop As you can clearly see the new .format() code is *much* slower than the old style % code. I recommend we spend some time on optimizing common code paths of the new .format() code. As first step I propose the move the __format__ method to a new type slot. __format__() is called for every object. My gut feeling says that a slot method is going to speed up the most common usage "{0}".format(some_string). Christian

11 years, 10 months

Any PEP about 2.6 -> 3000 code transition?

by Jesus Cea

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I can't find any PEP about detailed 2.6 -> 3000 migration guidelines, specially in the module (C code) extension area. Yes, I know about the 2to3 tool, but I'm interested in updating my 2.x code in order to keep (automatic via "2to3") difference between 2.x and 3.x codebase so small as possible. Also, 2to3 doesn't manage migration for C modules. Since I need to port bsddb3 to py3k, what I need to know?. Is any *updated* document out there?. PS: My plan is keep working in the python side under 2.x, and manage Python 3.0 via "2to3", for a long time. In the C side, I plan keeping the same codebase, with conditional compilation. Ideas?. - -- Jesus Cea Avion _/_/ _/_/_/ _/_/_/ jcea(a)jcea.es - http://www.jcea.es/ _/_/ _/_/ _/_/ _/_/ _/_/ jabber / xmpp:jcea@jabber.org _/_/ _/_/ _/_/_/_/_/ ~ _/_/ _/_/ _/_/ _/_/ _/_/ "Things are not so easy" _/_/ _/_/ _/_/ _/_/ _/_/ _/_/ "My name is Dump, Core Dump" _/_/_/ _/_/_/ _/_/ _/_/ "El amor es poner tu felicidad en la felicidad de otro" - Leibniz -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQCVAwUBSDjqJplgi5GaxT1NAQLP3QP/Y2bWmNzHKsIq23dRz9sxd237TSfzbs5X UzEQ6Ze9Kv1lRXYRfiGjk37aOeiO4xqoKPfASc/WjMN/TmRkUNZxMQEQWwFYhmCA aAVqGxNMEX3KCXvRP9MkkZYLPa9RZg8boPTMYCn+uLDW1Ff2Pwj96hFKbWKG0dkJ RamNp8BFhkM= =ngK+ -----END PGP SIGNATURE-----

11 years, 11 months

Deprecate parser's "ast" functions?

by Georg Brandl

The parser module exports each function and type twice, once with "AST" in the name, once with "ST". Since "AST" now has a different meaning for Python code compilation, I propose to deprecate the "ast" variants in 2.6 and remove them in Python 3000. (Also, all keyword arguments are called "ast", that cannot change in 2.6 but should in 3.0.) I'm at the moment changing the documentation of parser to only refer to the "st" variants anymore. Georg -- Thus spake the Lord: Thou shalt indent with four spaces. No more, no less. Four shall be the number of spaces thou shalt indent, and the number of thy indenting shall be four. Eight shalt thou not indent, nor either indent thou two, excepting that thou then proceed to four. Tabs are right out.

11 years, 11 months

Progress on switching Windows build to Berkeley DB 4.7.25...

by Trent Nelson

Hi all, Jesus, apologies that this has taken so long for me to get back to, I've been completely and utterly swamped with client work the past few weeks. However, thanks to a couple of hours spare at Detroit airport yesterday, I was finally able to make some progress on updating the Windows Berkeley DB build to 4.7.25. I've checked in the work I've done so far to branches/tnelson-trunk-bsddb-47-upgrade. One thing I wanted to double check with you is the following change: Modified: python/branches/tnelson-trunk-bsddb-47-upgrade/Lib/bsddb/test/test_replication.py ============================================================================== --- python/branches/tnelson-trunk-bsddb-47-upgrade/Lib/bsddb/test/test_replication.py (original) +++ python/branches/tnelson-trunk-bsddb-47-upgrade/Lib/bsddb/test/test_replication.py Wed Jun 18 06:13:44 2008 @@ -94,7 +94,7 @@ # The timeout is necessary in BDB 4.5, since DB_EVENT_REP_STARTUPDONE # is not generated if the master has no new transactions. # This is solved in BDB 4.6 (#15542). - timeout = time.time()+2 + timeout = time.time()+10 while (time.time()<timeout) and not (self.confirmed_master and self.client_startupdone) : time.sleep(0.02) if db.version() >= (4,6) : Basically, when using +2, the test failed every so often when running the entire test_bsddb3 suite. I picked 10 arbitrarily; it improves things, but it's still not 100%, I still encounter the following failure every so often: ====================================================================== ERROR: test01_basic_replication (bsddb.test.test_replication.DBReplicationManager) ---------------------------------------------------------------------- Traceback (most recent call last): File "s:\src\svn+ssh\pythondev@svn.python.org\python\branches\tnelson-trunk-bsddb-47-upgrade\lib\bsddb\test\test_replication.py", line 101, in setUp self.assertTrue(time.time()<timeout) AssertionError Can you comment on this? Apart from this small issue, the other 311 tests pass on x86 and x64 with flying colours, so nice work, whatever you've been doing ;-) Regards, Trent.

11 years, 11 months

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Python-Dev June 2008