[Python-Dev] distutils.sys: None in sys.modules

[Ka-Ping Yee]

On Tue, 10 Apr 2001, M.-A. Lemburg wrote:
> > What are 'distutils.sys', 'distutils.os', 'distutils.string',
> > 'distutils.re', 'distutils.distutils' doing in there? 
> > (The sys.modules dictionary maps all these keys to None.)
> 
> This basically means that the corresponding modules have already
> been loaded at top-level.

But there's no 'sys' module in the distutils package.
If there were one, it would be called 'distutils.sys'
everywhere, even within the distutils package, since
we decided that packages would always use absolute
module paths, right?

This behaviour seems quite confusing to me:

    localhost[1]% ls -al foo
    total 9
    drwxr-xr-x   2 ping     users        1024 Apr 10 04:50 ./
    drwxr-xr-x  12 ping     users        5120 Apr 10 04:49 ../
    -rw-r--r--   1 ping     users           0 Apr 10 04:49 __init__.py
    -rw-r--r--   1 ping     users         106 Apr 10 04:50 __init__.pyc
    -rw-r--r--   1 ping     users          50 Apr 10 04:50 sys.py
    -rw-r--r--   1 ping     users         216 Apr 10 04:50 sys.pyc
    localhost[2]% cat foo/sys.py
    import sys, os

    print 'here is foo.sys'

    blah = 1
    localhost[3]% python -S
    Python 2.1b2 (#28, Apr 10 2001, 02:49:05) 
    [GCC egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)] on linux2
    Type "copyright", "credits" or "license" for more information.
    >>> import sys, foo
    >>> sys.modules.keys()
    ['__main__', '__builtin__', 'sys', 'foo', 'signal', 'exceptions']
    >>> import foo.sys
    here is foo.sys
    >>> sys.modules.keys()
    ['os.path', 'os', 'foo', 'foo.sys', 'exceptions', '__main__', 'foo.os', 'posix', 'sys', '__builtin__', 'signal', 'UserDict', 'posixpath', 'stat']
    >>> sys.modules['foo.os']
    >>> sys.modules['foo.sys']
    <module 'foo.sys' from '/home/ping/python/foo/sys.py'>
    >>> import foo.os
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    ImportError: no module named 'os' could be found
    >>> import foo.sys

At this point sys.modules['foo.sys'] is a real module, as it should
be, but sys.modules['foo.os'] is None.  I don't see why 'foo.os'
should be present at all.


-- ?!ng

"All models are wrong; some models are useful."
    -- George Box