Issue 29031: 'from module import *' and all (original) (raw)

Issue29031

Created on 2016-12-21 08:13 by theller, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (4)
msg283721 - (view)	Author: Thomas Heller (theller) *	Date: 2016-12-21 08:13
The documentation states that 'from module import *' imports all symbols that are listed in the module's __all__ list. In Python 3, unlike Python 2, only symbols that do NOT start with an underscore are actually imported. The following code works in Python 2.7, but raises a NameError in Python 3.5: python -c "from ctypes.wintypes import *; print(_ULARGE_INTEGER)"
msg283734 - (view)	Author: Martin Panter (martin.panter) *	Date: 2016-12-21 10:02
Python 3 doesn’t have an __all__ list; it was removed in r85073 (Issue 3612). I don’t understand why it was removed. Maybe Hirokazu didn’t understand what it does. Since this is a regression, perhaps it should be added back.
msg283748 - (view)	Author: Eryk Sun (eryk sun)	Date: 2016-12-21 12:04
Python 3 does not skip names in __all__ that start with an underscore. wintypes in 2.x uses `from ctypes import *`, so it needs to define __all__. In 3.x it uses `import ctypes`, so it doesn't define __all__, and the private names _COORD, _FILETIME, _LARGE_INTEGER, _POINTL, _RECTL, _SMALL_RECT, and _ULARGE_INTEGER are skipped by a star import. That said, why are these private names (and also "tag" names) defined? And why isn't COORD defined instead of or in addition to _COORD?
msg283763 - (view)	Author: Thomas Heller (theller) *	Date: 2016-12-21 15:55
Thanks Martin and eryk for correcting me and finding the real cause of the problem. Am 21.12.2016 um 13:04 schrieb eryk sun: > ... the private names _COORD, _FILETIME, _LARGE_INTEGER, > _POINTL, _RECTL, _SMALL_RECT, and _ULARGE_INTEGER are skipped by a > star import. That said, why are these private names (and also "tag" > names) defined? And why isn't COORD defined instead of or in addition > to _COORD? These 'private' names and "tag" names were defined for compatibility with the windows SDK C header files. I didn't want to apply the Python 'private' convention to the C names, so they were added to the __all__ list. It was an oversight that COORD wasn't defined, I developed a different solution for the windows SDK names afterwards, but my code (which I'm porting to Python 3) still uses 'from ctypes.wintypes import *' and stumbled over the regression just now.