If you're reading this document, you probably have a good idea of what
modules, extensions, and so forth are. Nevertheless, just to be sure
that everyone is operating from a common starting point, we offer the
following glossary of common Python terms:
module
the basic unit of code reusability in Python: a block of
code imported by some other code. Three types of modules concern us
here: pure Python modules, extension modules, and packages.
pure Python module
a module written in Python and contained in a
single .py file (and possibly associated .pyc and/or
.pyo files). Sometimes referred to as a ``pure module.''
extension module
a module written in the low-level language of
the Python implementation: C/C++ for Python, Java for Jython.
Typically contained in a single dynamically loadable pre-compiled
file, e.g. a shared object (.so) file for Python extensions on
Unix, a DLL (given the .pyd extension) for Python extensions
on Windows, or a Java class file for Jython extensions. (Note that
currently, the Distutils only handles C/C++ extensions for Python.)
package
a module that contains other modules; typically contained
in a directory in the filesystem and distinguished from other
directories by the presence of a file __init__.py.
root package
the root of the hierarchy of packages. (This isn't
really a package, since it doesn't have an __init__.py
file. But we have to call it something.) The vast majority of the
standard library is in the root package, as are many small, standalone
third-party modules that don't belong to a larger module collection.
Unlike regular packages, modules in the root package can be found in
many directories: in fact, every directory listed in sys.path
contributes modules to the root package.
