[Python-Dev] Include datetime.py in stdlib or not? (original) (raw)

Alexander Belopolsky alexander.belopolsky at gmail.com
Tue Jul 13 21:52:44 CEST 2010

On Thu, Jul 8, 2010 at 3:09 PM, Brett Cannon <brett at python.org> wrote: ..

I can say that all the VM representatives have all said they like the idea.

This is encouraging. Here is an update on the status of datetime.py. I believe it is mostly ready to move from sandbox to py3k/Lib. The patch is available on the tracker at http://bugs.python.org/file17978/issue9206b.diff and on Rietveld at http://codereview.appspot.com/1824041 . Unfortunately since many changes are just file renames will minor code modifications, neither the patch nor Rietveld give a good overview of the proposed commit. I will try to give this overview here:

  1. Copy datetime.py from sandbox to py3k/Lib. (I need some help from an SVN expert on how to do that.) The diff between sandbox version and proposed commit is just

======================================================== --- ../py3k-datetime/datetime.py 2010-07-07 20:12:56.000000000 -0400 +++ Lib/datetime.py 2010-07-08 21:15:52.000000000 -0400 @@ -1555,7 +1555,6 @@ @classmethod def strptime(cls, date_string, format): 'string, format -> new datetime parsed from a string (like time.strptime()).'

@@ -1874,6 +1873,13 @@ timezone.min = timezone(timezone._minoffset) timezone.max = timezone(timezone._maxoffset)

+try: + from _datetime import * +except ImportError: + pass + +import _strptime +

The "from _datetime import *" is the standard fast implementation override and "import _strptime" had to be moved from function level to module level after class definitions due to circular dependency of _strptime on datetime.

The best place to review the entire datetime.py is on Rietveld at http://codereview.appspot.com/1824041/diff/1/4. I have only one remaining issue with this code - it leaves a number of "private" _xyz functions in the datetime module that are neither used nor overridden by the C implementation. In my view, this is not a big issue, but it can be dealt with by either moving module level functions to class namespace (making them static or class methods as appropriate) or by deleting them explicitly in the else clause of the try statement that imports the fast overrides.

  1. Rename datetimemodule.c to _datetimemodule.c. The code changes are trivial: module name and the name of the init function. http://codereview.appspot.com/1824041/diff/1/7

  2. Rename test_datetime.py to datetimetester.py. The testing strategy implements Nick Coghlan's idea of importing the test classes from a tester module with and without _datetime and injecting them into test_datetime namespace under different names. http://mail.python.org/pipermail/python-dev/2010-July/101598.html

The changes required to the code are minimal: http://codereview.appspot.com/1824041/diff/1/5 .

  1. Add new test_datetime.py that contains somewhat elaborate import machinery to create duplicates of each test case from datetimetester.py running with and without datetime acceleration.

Unfortunately, test_datetime.py did not make it to Rietveld, but it is small enough to include here:

================================================ import unittest import sys from test.support import import_fresh_module, run_unittest TESTS = 'test.datetimetester' pure_tests = import_fresh_module(TESTS, fresh=['datetime', '_strptime'], blocked=['_datetime']) fast_tests = import_fresh_module(TESTS, fresh=['datetime', '_datetime', '_strptime'])

test_modules = [pure_tests, fast_tests] test_suffixes = ["_Pure", "_Fast"]

for module, suffix in zip(test_modules, test_suffixes): for name, cls in module.dict.items(): if isinstance(cls, type) and issubclass(cls, unittest.TestCase): name += suffix cls.name = name globals()[name] = cls def setUp(self, module=module, setup=cls.setUp): self._save_sys_modules = sys.modules.copy() sys.modules[TESTS] = module sys.modules['datetime'] = module.datetime_module sys.modules['_strptime'] = module.datetime_module._strptime setup(self) def tearDown(self, teardown=cls.tearDown): teardown(self) sys.modules.init(self._save_sys_modules) cls.setUp = setUp cls.tearDown = tearDown

def test_main(): run_unittest(name)

if name == "main": test_main()

Since this change does not introduce any new features, I think it is safe to commit it and make further improvements to datetime.py (if any) once it is in the main tree.

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