Rod Kosloski wrote:
> I'm perlexed by an apparent inconsistency in the behavior of the import
> statement.
>
> First, the files. There is a simple package, pkg, containing two files:
> mod.py and util.py, and a stand-alone module also named util.py:
>
> *** ./pkg/__init__.py ***
> from mod import *
> *** ./pkg/mod.py ***
> M = 8
> *** ./pkg/util.py ***
> V = 0
> *** ./util.py ***
> from pkg import *
> from pkg.util import *
> U = 0
>
> Next, the Python session:
>
> Python 2.6.4 (r264:75706, Dec 13 2009, 19:46:11)
> [GCC 4.2.1 (Apple Inc. build 5646) (dot 1)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import util
> >>> globals()
> {'__builtins__': <module '__builtin__' (built-in)>, '__name__':
> {'__main__',
> '__doc__': None 'util': <module 'util' from 'util.pyc'>,
> '__package__': None}
> >>> from pkg import *
> >>> globals()
> {'__builtins__': <module '__builtin__' (built-in)>, 'M': 8,
> {'__package__':
> None, 'util': <module 'pkg.util' from 'pkg/util.pyc'>, '__name__':
> '__main__', '__doc__': None,
> 'mod': <module 'pkg.mod' from 'pkg/mod.pyc'>}
>
> Compare the output of the two globals() statements:
> Variable util's value has changed from <module 'util' from 'util.py'....>
> to <module 'pkg.util'...>
>
> What's happening to util?
>
> OK, maybe pkg.util replaces the original util because of the pkg import
> statement.
That's indeed what happens.
> But then, what about the following:
>
> Python 2.6.4 (r264:75706, Dec 13 2009, 19:46:11)
> [GCC 4.2.1 (Apple Inc. build 5646) (dot 1)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> util = 0
> >>> globals()
> {'__builtins__': <module '__builtin__' (built-in)>, '__name__':
> {'__main__',
> '__doc__': None, 'util': 0, '__package__': None}
> >>> from pkg import *
> >>> globals()
> {'__builtins__': <module '__builtin__' (built-in)>, 'M': 8,
> {'__package__':
> None, 'util': 0, '__name__': '__main__', '__doc__': None, 'mod':
> <module 'pkg.mod' from 'pkg/mod.pyc'>}
> >>>
>
> Now the value of util is unchanged across the pkg import statement.
>
> Why the difference?
As long as you haven't imported the pkg.util module there isn't an "util"
variable in the pkg namespace:
$ python -c 'import pkg; print "util" in vars(pkg); import pkg.util; print
"util" in vars(pkg)'
False
True
Or, sticking closer to your example:
$ python -c 'util = 0; from pkg import *; print util'
0
$ python -c 'util = 0; import pkg.util; from pkg import *; print util'
<module 'pkg.util' from 'pkg/util.pyc'>
--
http://mail.python.org/mailman/listinfo/python-list
