Getting Pypy to recognize third party modules

python pypy pytables
jab picture jab · Jun 25, 2012 · Viewed 13.9k times · Source

Just a quick question, how do I get pypy to recognize third pary modules that I have in Python? For instance, I get the following error.

from tables import *
ImportError: No Module named tables

Which is basically saying that it cannot find my pytables library that I use to interact with in the script I am trying to run.

Answer

user1277476 picture user1277476 · Jun 25, 2012

For pure python modules, just add the directory containing the modules to your sys.path, using something like:

sys.path.insert(0, '/usr/local/lib')
sys.path.insert(0, os.path.expanduser('~/lib'))

This works for CPython, Pypy and Jython.

For C extension modules, you can try Pypy's cpyext, but it won't run everything you might hope for, because some CPython C extension modules wander into dark corners of CPython's C-based runtime: http://morepypy.blogspot.com/2010/04/using-cpython-extension-modules-with.html

I sometimes write code that uses ctypes to interface with a C .so, and then use that on both CPython and Pypy, because they both do pretty well with ctypes - but ctypes can be kinda slow on CPython: http://docs.python.org/library/ctypes.html Last I checked, Jython had the beginnings of ctypes, but it wasn't far enough along to use, at least not for my purposes.

There's also a new interface that requires a C compiler at runtime. It'll likely be less brittle (read: prone to segfaults) than ctypes. It's described here: http://morepypy.blogspot.com/2012/06/release-01-of-cffi.html It comes from the Pypy project I believe, but it was made to work first on CPython. AFAIK, it doesn't yet run on Pypy.

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