Mysterious non-module A.sys

[Robin Becker]

I have a package A containing a null __init__.py and a simple module B.py

C:\code>cat A\B.py
import sys
print __file__
print sys.modules.keys()

C:\code>python -c"import A.B"
A\B.py
['copy_reg', 'A.B', 'locale', '__main__', 'site', '__builtin__', 'encodings',
'os.path', 'A.sys', 'encodings.codecs', 'ntpath', 'UserDict',
'encodings.exceptions', 'nt', 'A', 'stat', 'zipimport', 'warnings',
'encodings.types', '_codecs', 'encodings.cp1252', 'sys', 'codecs', 'types',
'_locale', 'signal', 'linecache', 'encodings.aliases', 'exceptions', 'os']

C:\code>

where does A.sys come from? I tried an experiment and it seems that it's the
import statement in B.py so if I changed that to import sys,socket I also get
A.socket so I assume it's the import within import that causes these strange
modules to appear.

Strangely, attempts to import A.sys fail and its value in sys.modules is None.
What is the entry for?