2.2 General Python terminology
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:
- 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 implemention: C/C++ for CPython, Java for JPython.
Typically contained in a single dynamically loadable pre-compiled
file, e.g. a shared object (.so) file for CPython extensions on
Unix, a DLL (given the .pyd extension) for CPython extensions
on Windows, or a Java class file for JPython extensions. (Note that
currently, the Distutils only handles C/C++ extensions for CPython.)
- 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
can contribute modules to the root package.
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