python如何导入具有多个副本的软件包

Question

I was believing that when importing a package, it would search from sys.path and use the first hit for import. However, it seems not true:

import mpl_toolkits
print(mpl_toolkits.__path__)

And it outputs:

['/Library/Python/2.7/site-packages/matplotlib-1.5.0-py2.7-macosx-10.11-intel.egg/mpl_toolkits', '/usr/local/lib/python2.7/site-packages/mpl_toolkits']

Can someone please explain to me how exactly python looks for packages if it is installed multiple times in the machine (in different location searchable by sys.path )? Or a pointer to relevant reference would be good.

Answer 1

when you import a module, python uses PYTHON PATH (system variable that contains a list of folders) and loops to search for importable module.
Python will test if it is a package (folder containing init .py) or a module (*.py). it will stop on first module found if no module is found python raises an import error