Python: Essential Reference, Third Edition

Module Loading and Compilation

So far, this chapter has presented modules as files containing Python code. However, modules loaded with import really fall into four general categories:

• Code written in Python (.py files)

• C or C++ extensions that have been compiled into shared libraries or DLLs

• Packages containing a collection of modules

• Built-in modules written in C and linked into the Python interpreter

When looking for a module (for example, foo), the interpreter searches each of the directories in sys.path for the following files (listed in search order):

1. A directory, foo, defining a package.

2. foo.so, foomodule.so, foomodule.sl, or foomodule.dll (compiled extensions).

3. foo.pyo (only if the -O or -OO option has been used).

4. foo.pyc.

5. foo.py. (On Windows, ...