[Q] module name available in 'from ... import ...' statement

[kwatch]

What is the condition of module name which is available in
'from .. import ..' statement ?

    ----------------------------------------
    import os
    print os.path              # <module 'posixpath' from '/usr/local/
lib/python2.5/posixpath.pyc'>
    from posixpath import sep  # (no errors)
    from os.path import sep    # (no errors, wow!)
    path = os.path
    from path import sep       # ImportError: No module named path
    ----------------------------------------

I found that library 'os.py' exists but 'os/path.py' doesn't exist
in '/usr/local/lib/python2.5'.
It means that file 'os/path.py' is not required to perform
'from os.path import sep' statement.

Could you teach me the condition of module name which is available
in 'from ... import ...' statement?

The goal what I want to do is to create a module by 'new' module
and specify that module name in 'from ...' statement.

    ----------------------------------------
    # create a module
    import new
    foo = new.module('foo')
    foo.pi = 3.14159
    foo.x2 = lambda x: 2*x
    # specify it in 'from' statement
    from foo import pi, x2     # ImportError: No module named foo
    ----------------------------------------


--
regards,
kwatch