Python-Dev December 2007

python-dev@python.org

74 participants
85 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

11 years

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, 2 months

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, 5 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, 5 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, 9 months

Adventures with x64, VS7 and VS8 on Windows

by Mark Hammond

Hi all, I hope the cross-post is appropriate. I've started playing with getting the pywin32 extensions building under the AMD64 architecture. I started building with Visual Studio 8 (it was what I had handy) and I struck a few issues relating to the compiler version that I thought worth sharing. * In trying to build x64 from a 32bit VS7 (ie, cross-compiling via the PCBuild directory), the python.exe project fails with: pythoncore fatal error LNK1112: module machine type 'X86' conflicts with target machine type 'AMD64' is this a known issue, or am I doing something wrong? * The PCBuild8 project files appear to work without modification (I only tried native compilation here though, not a cross-compile) - however, unlike the PCBuild directory, they place all binaries in a 'PCBuild8/x64' directory. While this means that its possible to build for multiple architectures from the same source tree, it makes life harder for tools like 'distutils' - eg, distutils already knows about the 'PCBuild' directory, but it knows nothing about either PCBuild8 or PCBuild8/x64. A number of other build processes also know to look inside a PCBuild directory (eg, Mozilla), so instead of formalizing PCBuild8, I think we should merge PCBuild8 into PCBuild. This could mean PCBuild/vs7 and PCBuild/vs8 directories with the "project" files, but binaries would still be generated in the 'PCBuild' (or PCBuild/x64) directory. This would mean the same tree isn't capable of hosting 2 builds from different VS compilers, but I think that is reasonable (if it's a problem, just have multiple source directories). I understand that PCBuild8 is not "official", but in the assumption that future versions of Python will use a compiler later than VS7, it makes sense to me to clean this up now - what are others opinions on this? * Re the x64 directory used by the PCBuild8 process. IMO, it makes sense to generate x64 binaries to their own directory - my expectation is that cross-compiling between platforms is a reasonable use-case, and we should support multiple achitectures for the same compiler version. This would mean formalizing the x64 directory in both 'PCBuild' and distutils, and leaving other external build processes to update as they support x64 builds. Does this make sense? Would this fatally break other scripts used for packaging (eg, the MSI framework)? * Wide characters in VS8: PC/pyconfig.h defines PY_UNICODE_TYPE as 'unsigned short', which corresponds with both 'WCHAR' and 'wchar' in previous compiler versions. VS8 defines this as wchar_t, which I'm struggling to find a formal definition for beyond being 2 bytes. My problem is that code which assumes a 'Py_UNICODE *' could be used in place of a 'WCHAR *' now fails. I believe the intent on Windows has always been "PyUNICODE == 'native unicode'" - should PC/pyconfig.h reflect this (ie, should pyconfig.h grow a version specific definition of PyUNICODE as wchar_t)? * Finally, as something from left-field which may well take 12 months or more to pull off - but would there be any interest to moving the Windows build process to a cygwin environment based on the existing autoconf scripts? I know a couple of projects are doing this successfully, including Mozilla, so it has precendent. It does impose a greater burden on people trying to build on Windows, but I'd suggest that in recent times, many people who are likely to want to build Python on Windows are already likely to have a cygwin environment. Simpler mingw builds and nuking MSVC specific build stuff are among the advantages this would bring. It is not worth adding this as "yet another windows build option" - so IMO it is only worth progressing with if it became the "blessed" build process for windows - if there is support for this, I'll work on it as the opportunity presents itself... I'm (obviously) only suggesting we do this on the trunk and am happy to make all agreed changes - but I welcome all suggestions or critisisms of this endeavour... Cheers, Mark

12 years, 6 months

Re: [Python-Dev] [Python-checkins] r45510 - python/trunk/Lib/pkgutil.py python/trunk/Lib/pydoc.py

by M.-A. Lemburg

Phillip.eby wrote: > Author: phillip.eby > Date: Tue Apr 18 02:59:55 2006 > New Revision: 45510 > > Modified: > python/trunk/Lib/pkgutil.py > python/trunk/Lib/pydoc.py > Log: > Second phase of refactoring for runpy, pkgutil, pydoc, and setuptools > to share common PEP 302 support code, as described here: > > http://mail.python.org/pipermail/python-dev/2006-April/063724.html Shouldn't this new module be named "pkglib" to be in line with the naming scheme used for all the other utility modules, e.g. httplib, imaplib, poplib, etc. ? > pydoc now supports PEP 302 importers, by way of utility functions in > pkgutil, such as 'walk_packages()'. It will properly document > modules that are in zip files, and is backward compatible to Python > 2.3 (setuptools installs for Python <2.5 will bundle it so pydoc > doesn't break when used with eggs.) Are you saying that the installation of setuptools in Python 2.3 and 2.4 will then overwrite the standard pydoc included with those versions ? I think that's the wrong way to go if not made an explicit option in the installation process or a separate installation altogether. I bothered by the fact that installing setuptools actually changes the standard Python installation by either overriding stdlib modules or monkey-patching them at setuptools import time. > What has not changed is that pydoc command line options do not support > zip paths or other importer paths, and the webserver index does not > support sys.meta_path. Those are probably okay as limitations. > > Tasks remaining: write docs and Misc/NEWS for pkgutil/pydoc changes, > and update setuptools to use pkgutil wherever possible, then add it > to the stdlib. Add setuptools to the stdlib ? I'm still missing the PEP for this along with the needed discussion touching among other things, the change of the distutils standard "python setup.py install" to install an egg instead of a site package. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Apr 18 2006) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ ::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! ::::

12 years, 6 months

complaints..

by Jay

I'm sure you've heard most/all of this before but..it..just..seems..so..true... Finally this week I've "written" (ported from sh) a bunch of Perl, 2000 sparse lines. While it sure beats Perl, it has some glaring flaws, more glaring due to its overall goodness. I feel compelled to voice my opinion, as if we don't live in a benevolent dictatorship :), and as if the weight of existing code was zero. Much of what I dislike cannot be changed without massive breakage. Below is what i get from: jbook:/dev2/cm3/scripts/python/flaws jay$ ls -l total 72 -rw-r--r-- 1 jay admin 834 Dec 29 16:02 1_not_lexically_scoped.py -rw-r--r-- 1 jay admin 238 Dec 29 16:02 2_reads_scoped_writes_not.py -rw-r--r-- 1 jay admin 593 Dec 29 16:02 3_lambda_is_neutered.py -rw-r--r-- 1 jay admin 377 Dec 29 16:03 4_assignment_is_not_expression.py -rw-r--r-- 1 jay admin 760 Dec 29 16:02 5_for_loop_off_by_one.py -rw-r--r-- 1 jay admin 412 Dec 29 16:01 6_docs_good_but_a_complaint.txt -rw-r--r-- 1 jay admin 254 Dec 29 16:02 7_print_is_wierd.py -rw-r--r-- 1 jay admin 286 Dec 29 16:06 8_eval_vs_exec.py -rw-r--r-- 1 jay admin 824 Dec 29 16:14 9_typo_on_read_error_but_write_ok.py jbook:/dev2/cm3/scripts/python/flaws jay$ cat * > all.txt jbook:/dev2/cm3/scripts/python/flaws jay$ edit all.txt Each "---" seperates a file and they are executable Python. - Jay #---------------------------------------------------------- # flaw #1 # not lexically scopied # Functions have their own locals, but other blocks do not. # This is true both for "normal" variables and lexically nested functions. # # # This is probably largely an outcome of not declaring variables? # A = "A1:global" def F1(): A = "A1:in first F1" print "F1:global" if True: A = "A1:in if" def F1(): A = "A1:in if.F1" # This does the right thing. print "F1:in if" F1() # This does the right thing. # This should go to "global" but it goes to "in if" F1() def F2(): A = "A1:in F2" def F1(): A = "A1:in F2.F1" print "F1:in F2" # Given how if behaved, you'd expect this to go to F2.F1 but it does not. F1() # This should be "global" but is "in if". print("A is " + A) #---------------------------------------------------------- # flaw #2 # # In functions, reads are scoped. Writes are not. # A = "1" def F1(): A = "2" # not an error def F2(): #B = A # error A = "3" F1() F2() print(A) #---------------------------------------------------------- # flaw #3: # lambda is neutered # It allows just one expression, and no statements # # This should work: import os #os.path.walk( # "..", # lambda(a, b, c): # print(b) # print(b) # None) # Instead I must say: def Callback(a, b, c): print(b) print(b) os.path.walk( "..", Callback, None) # # Moving callbacks away from their point of use hurts readability. # This is probably mitigated by lexical scoping of functions, but # notice that other blocks are not lexically scoped. # #---------------------------------------------------------- # flaw #4: # assignment is not an expression # # This should work (seen in Perl code, nice idiom): #A = [1,2] #while (B = A.pop()): # print(B) # instead I must say: A = [1,2] while (A): B = A.pop() print(B) # Even if you reject popping an empty list, ok # there are PLENTY of applications of this. #---------------------------------------------------------- # flaw #5 # # for loops suck # # It should be easy to iterate from 0 to n, not 0 to n - 1, # thereby knowing why the loop terminated # #This should work: # print the first even number, if there are any A = [1, 3] for i in range(0, len(A)): if ((A[i] % 2) == 0): print("even number found") break; if (i == len(A)): print("no even numbers found") # instead I must write: i = 0 while (i != len(A)): if ((A[i] % 2) == 0): print("even number found") break; i += 1 if (i == len(A)): print("no even numbers found") # with the attendent problem of not being able to "continue" ever, since # the end of the loop body must be run in order to proceed Flaw #6 The docs are very good. However the reference doesn't give much in the way of semantic description. It is surprising that an experienced programmer MUST depend on the tutorial or any examples or semantics. Light on examples, ok for reference. The language reference is little more than the grammar in parts. There needs to be links from the reference back to the tutorial. Perhaps merge the indices for Tutorial, Language Reference, Library Reference. Or maybe that's what search is for. On the other hand, way better than Perl. #---------------------------------------------------------- # Flaw #7 # # This is a compatibility issue. # print is both a statement and a function, or something. # print() # should print just a newline, but prints two parens # workaround: print("") #---------------------------------------------------------- # flaw #8 # # Having to eval expressions but exec statements feels wrong. # There should just be eval. # # eval("print(1)") # error exec("print(1)") # not an error exec("1 + 2") # not an error? eval("1 + 2") # not an error #---------------------------------------------------------- # flaw #9 # # Python protects me, via early checking, from typos # when I read, but not when I write. It should do both. # That is, I should declare variables. # Correct = 1 # proposed typo is Corect #A = Corect # error, good Corect = 1 # no error, bad # For classes, by default, same thing: class Foo(object): def __init__(self): self.Correct =1 F = Foo() # print(F.Corect) # error, good F.Corect = 1 # no error, bad # __slots__ fixes this, but is not the default class Bar(object): __slots__ = ["Correct"] def __init__(self): self.Correct =1 B = Bar() # print(B.Corect) # error, good #B.Corect = 1 # error, good # __slots__ should be the default and then some other syntax # for "expandable" types, like __slots__ = [ "*" ] _________________________________________________________________ Get the power of Windows + Web with the new Windows Live. http://www.windowslive.com?ocid=TXT_TAGHM_Wave2_powerofwindows_122007

12 years, 8 months

test_sys failures

by Guido van Rossum

When I build from scratch and run most tests (regrtest.py -uall) I get some strange failures with test_sys.py: test test_sys failed -- Traceback (most recent call last): File "/usr/local/google/home/guido/python/py3kd/Lib/test/test_sys.py", line 302, in test_43581 self.assertEqual(sys.__stdout__.encoding, sys.__stderr__.encoding) AssertionError: 'ascii' != 'ISO-8859-1' The same test doesn't fail when run in isolation. Interestingly, I saw this with 2.5 as well as 3.0, but not with 2.6! Any ideas? -- --Guido van Rossum (home page: http://www.python.org/~guido/)

12 years, 8 months

Extend reST spec to allow automatic recognition of identifiers in comments?

by Jameson "Chema" Quinn

This is a VERY VERY rough draft of a PEP. The idea is that there should be some formal way that reST parsers can differentiate (in docstrings) between variable/function names and identical English words, within comments. PEP: XXX Title: Catching unmarked identifiers in docstrings Version: 0.0.0.0.1 Last-Modified: 23-Aug-2007 Author: Jameson Quinn <firstname dot lastname at gmail> Status: Draft Type: Informational Content-Type: text/x-rst Created: 23-Aug-2007 Post-History: 30-Aug-2002 Abstract ======== This PEP makes explicit some additional ways to parse docstrings and comments for python identifiers. These are intended to be implementable on their own or as extensions to reST, and to make as many existing docstrings as possible usable by tools that change the visible representation of identifiers, such as translating (non-english) code editors or visual programming environments. Docstrings in widely-used modules are encouraged to use \`explicit backquotes\` to mark identifiers which are not caught by these cases. THIS IS AN EARLY DRAFT OF THIS PEP FOR DISCUSSION PURPOSES ONLY. ALL LOGIC IS INTENTIONALLY DEFINED ONLY BY EXAMPLES AND THERE IS NO REFERENCE IMPLEMENTATION UNTIL A THERE ARE AT LEAST GLIMMERINGS OF CONSENSUS ON THE RULE SET. Rationale ========= Python, like most computer languages, is based on English. This can represent a hurdle to those who do not speak English. Work is underway on Bityi_, a code viewer/editor which translates code to another language on load and save. Among the many design issues in Bityi is that of identifiers in docstrings. A view which translates the identifiers in code, but leaves the untranslated identifier in the docstrings, makes the docstrings worse than useless, even if the programmer has a rudimentary grasp of English. Yet if all identifiers in docstrings are translated, there is the problem of overtranslation in either direction. It is necessary to distinguish between the variable named "variable", which should be translated, and the comment that something is "highly variable", which should not. .. _Bityi: http://wiki.laptop.org/go/Bityi Note that this is just one use-case; syntax coloring and docstring hyperlinks are another one. This PEP is not the place for a discussion of all the pros and cons of a translating viewer. PEP 287 standardizes reST as an optional way to markup docstrings. This includes the possibility of using \`backquotes\` to flag Python identifiers. However, as this PEP is purely optional, there are many cases of identifiers in docstrings which are not flagged as such. Moreover, many of these unflagged cases could be caught programatically. This would reduce the task of making a module internationally-viewable, or hyperlinkable, considerably. This syntax is kept relatively open to allow for reuse with other programming languages. Common cases of identifiers in docstrings ========================================= The most common case is that of lists of argument or method names. We call these "identifier lists":: def register(func, *targs, **kargs): """register a function to be executed someday func - function to be called targs - optional arguments to pass kargs - optional keyword arguments to pass """ #func, targs, and kargs would be recognized as identifiers in the above. class MyClass(object): """Just a silly demonstration, with some methods: thisword : is a class method and you can call it - it may even return a value. As with reST, the associated text can have several paragraphs. BUT - you can't nest this construct, so BUT isn't counted. anothermethod: is another method. eventhis -- is counted as a method. anynumber --- of dashes are allowed in this syntax But consider: two words are NOT counted as an identifier. things(that,look,like,functions): are functions (see below) Also, the docstring may have explanatory text, below or by itself: so we have to deal with that. Thus, any paragraph which is NOT preceded by an empty line or another identifier list - like "itself" above - does not count as an identifier. """ #thisword, anothermethod, eventhis, anynumber, and things would be #recognized as identifiers in the above. Another case is things which look like functions, lists, indexes, or dicts:: """ afunction(is,a,word,with,parentheses) [a,list,is,a,bunch,of,words,in,brackets] anindex[is, like, a, cross, between, the, above] {adict:is,just:words,in:curly, brackets: likethis} """ #all of the above would be recogniszed as identifiers. The "syntax" of what goes inside these is very loose. identifier_list ::= [<initial_word>]<opening_symbol> <content_word> {<separator_symbol> <content_word>} <closing symbol> , with no whitespace after initial_word, and where separator_symbol is the set of symbols ".,<>{}[]+-*^%=|/()[]{}" MINUS closing_symbol. content_word could maybe be a quoted string, too. In the "function name", no whitespace is allowed, but the symbols ".,*^=><-" are. Thus:: """ this.long=>function.*name(counts, and: so |do| these {so-called] arguments) {but,you - cant|use[nested]brackets{so,these,are.identifiers }but,these,arent} {heres.an.example.of."a string, no identifiers in here",but.out.here.yes } { even.one.pair.of.words.with.no symbols.means.nothing.here.is.an.identifier} Any of these structures that open on one line {but.close.on. the.next} are NOT counted as identifiers. """ #in the above: lines 1,2,and the parts of 3 outside the quotes #would be recognized as identifiers The above flexibility is intended to cover the various possibilities for argument lists in a fair subset of other languages. Languages which use only whitespace for argument separation are not covered by these rules. The final case is words that are in some_kind of mixedCase. These are only optionally counted as identifiers if they are also present as an identifier OUTSIDE the comments somewhere in the same file. Doctest and preformatted reST sections should be considered as 100% python code and treated as identifiers (or keywords). Recommended use =============== The rules above are designed to catch the large majority of identifiers already present in docstrings, while applying only extremely rarely to words that should properly be considered as natural language. However, they are inevitably imperfect. All docstrings of modules intended for wide use should manually fix all cases in which these rules fail. If the rules underapply, you can use either \`back quotes\` or parentheses() to mark words as identifiers; if they overapply and reformatting tricks don't fix the problem, <SOME DIRECTIVE TO TURN OFF ALL THIS LOGIC FOR A STRING> Optional use inside comments or non-docstring strings ===================================================== Comments -------- Comments or blocks of comments alone on consecutive lines should be able, optionally, to use these same tricks to spotlight identifiers. Other strings ------------- I'm not sure yet what the rules should be here. One option I'm considering is to be able to turn on all the above logic with some evil hack such as '' 'a string like this, concatenated with an empty string'. 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 coding: utf-8 End:

12 years, 8 months

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Python-Dev December 2007