[Python-Dev] importlib hooray!

Thomas Heller theller at ctypes.org
Wed Feb 6 10:26:38 CET 2013

I have become a fan of the new python 3.3 importlib
in the last few days.

It has allowed me to write a ModuleMapper which I put into
sys.metapath (in sitecustomize.py, for Python 3.3).

This mapper currently does rename modules like 'Queue' or '_winreg'
to the Python3 modules 'queue' or 'winreg' without the need to change
my 2.7 sourcecode (changing the sourcecode is required when using
six.moves to write 2.x/3.x compatible code).

The six.moves approach has another problem with freeze tools (py2exe
for example):  ModuleFinder does not find the moved modules because
it cannot track __import__().

I have also started a new modulefinder which uses importlib to find
modules; this was quite easy since I could copy a lot of code from
importlib._bootstrap.  The great thing is that this new modulefinder
is much better than the old one:  It finds modules in zipped eggs
or other zip-archives which are on sys.path; also it finds the renamed
modules correctly that my ModuleMapper has mapped.

The only thing that I am missing is that it is a bit of guesswork to
find out the type of the module that importlib.find_loader() has found.

Previously imp.find_module returned a tuple containing the type of
module found (like imp.PY_SOURCE), I have to poke around in some
attributes of the result of importlib.find_loader() to guess the type.


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