Python: List Modules, Search Path, Loaded Modules

List Available Modules

To list all modules, type pydoc modules in terminal.

or in Python

print (help('modules') )

# -*- coding: utf-8 -*-

# prints a list of existing modules
print(help('modules'))

Please wait a moment while I gather a list of all available modules...

CDROM               binhex              itertools           site
DLFCN               bisect              json                sitecustomize
IN                  builtins            keyword             smtpd
TYPES               bz2                 lib2to3             smtplib
...

Note: in Ubuntu Linux, as of 2013-11-25, there's a bug that both pydoc modules and help('modules') will crash Python. Use python3 instead.

sudo apt-get install python3

pydoc3 modules

Reading Module Documentation

To read the doc of a module, in terminal, type pydoc module_name, or in Python program call help(module_name).

# -*- coding: utf-8 -*-
# python

import os

# print the module's online manual
print help(os)

Note: the documentation from pydoc is not identical to the official documentation. Doc from pydoc is generated from the module source code, and is terse and technical.

List Module's Function/Variable Names

• dir(module_name) → list all names exported by the module module_name.
• dir() → list all names in current scope (but not standard functions). To list standard functions, import __builtin__ first, then dir(__builtin__).

# -*- coding: utf-8 -*-
# python

import re

# print all names exported by the module
print dir(re)

# sample output:

# ['DEBUG', 'DOTALL', 'I', 'IGNORECASE', 'L', 'LOCALE', 'M', 'MULTILINE', 'S', 'Scanner', 'T', 'TEMPLATE', 'U', 'UNICODE', 'VERBOSE', 'X', '_MAXCACHE', '__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__version__', '_alphanum', '_cache', '_cache_repl', '_compile', '_compile_repl', '_expand', '_locale', '_pattern_type', '_pickle', '_subx', 'compile', 'copy_reg', 'error', 'escape', 'findall', 'finditer', 'match', 'purge', 'search', 'split', 'sre_compile', 'sre_parse', 'sub', 'subn', 'sys', 'template']

Using Module

import module_name → load a module.

module_name.function_name → call a function in module.

# -*- coding: utf-8 -*-
# python

# import the standard module named os

import os

# example of using a function
print 'current dir is:', os.getcwd()

Import Function Names from Module

Module's function name can be imported directly by the syntax:

• from module_name import name_1, name_2, … → import several functions.
• from module_name import * → import all functions.

# -*- coding: utf-8 -*-
# python

from os import getcwd
print getcwd()  # current working dir

Default “module”

All global (variable/function) names in Python are considered to be in the pseudo-module namespace named __main__.

# -*- coding: utf-8 -*-
# python

print dir() # ['__builtins__', '__doc__', '__file__', '__name__', '__package__']

print dir("__main__")

# ['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

Module Search Paths

Python module search paths is stored in the variable sys.path.

# -*- coding: utf-8 -*-
# python

import sys
import pprint

# pretty print module search paths
pprint.pprint(sys.path)

# sample output
"""
['/home/joe/web/',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gst-0.10',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/pymodules/python2.7',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client',
 '/usr/lib/python2.7/dist-packages/ubuntuone-client',
 '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel',
 '/usr/lib/python2.7/dist-packages/ubuntuone-couch',
 '/usr/lib/python2.7/dist-packages/ubuntuone-installer',
 '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol']
"""

List Loaded Modules

Loaded module names is stored in the variable sys.modules.

# -*- coding: utf-8 -*-
# python

import sys
import pprint

# pretty print loaded modules
pprint.pprint(sys.modules)

# sample output
"""
{'UserDict': <module 'UserDict' from '/usr/lib/python2.7/UserDict.pyc'>,
 '__builtin__': <module '__builtin__' (built-in)>,
 '__main__': <module '__main__' from '/home/joe/web/test.py'>,
 '_abcoll': <module '_abcoll' from '/usr/lib/python2.7/_abcoll.pyc'>,
 '_codecs': <module '_codecs' (built-in)>,
 '_sre': <module '_sre' (built-in)>,
 '_warnings': <module '_warnings' (built-in)>,
 '_weakref': <module '_weakref' (built-in)>,
 '_weakrefset': <module '_weakrefset' from '/usr/lib/python2.7/_weakrefset.pyc'>,
 'abc': <module 'abc' from '/usr/lib/python2.7/abc.pyc'>,
 'apport_python_hook': <module 'apport_python_hook' from '/usr/lib/python2.7/dist-packages/apport_python_hook.pyc'>,
 'cStringIO': <module 'cStringIO' (built-in)>,
 'codecs': <module 'codecs' from '/usr/lib/python2.7/codecs.pyc'>,
 'copy_reg': <module 'copy_reg' from '/usr/lib/python2.7/copy_reg.pyc'>,
 'encodings': <module 'encodings' from '/usr/lib/python2.7/encodings/__init__.pyc'>,
 'encodings.__builtin__': None,
 'encodings.aliases': <module 'encodings.aliases' from '/usr/lib/python2.7/encodings/aliases.pyc'>,
 'encodings.codecs': None,
 'encodings.encodings': None,
 'encodings.utf_8': <module 'encodings.utf_8' from '/usr/lib/python2.7/encodings/utf_8.pyc'>,
 'errno': <module 'errno' (built-in)>,
 'exceptions': <module 'exceptions' (built-in)>,
 'genericpath': <module 'genericpath' from '/usr/lib/python2.7/genericpath.pyc'>,
 'linecache': <module 'linecache' from '/usr/lib/python2.7/linecache.pyc'>,
 'os': <module 'os' from '/usr/lib/python2.7/os.pyc'>,
 'os.path': <module 'posixpath' from '/usr/lib/python2.7/posixpath.pyc'>,
 'posix': <module 'posix' (built-in)>,
 'posixpath': <module 'posixpath' from '/usr/lib/python2.7/posixpath.pyc'>,
 'pprint': <module 'pprint' from '/usr/lib/python2.7/pprint.pyc'>,
 're': <module 're' from '/usr/lib/python2.7/re.pyc'>,
 'signal': <module 'signal' (built-in)>,
 'site': <module 'site' from '/usr/lib/python2.7/site.pyc'>,
 'sitecustomize': <module 'sitecustomize' from '/usr/lib/python2.7/sitecustomize.pyc'>,
 'sre_compile': <module 'sre_compile' from '/usr/lib/python2.7/sre_compile.pyc'>,
 'sre_constants': <module 'sre_constants' from '/usr/lib/python2.7/sre_constants.pyc'>,
 'sre_parse': <module 'sre_parse' from '/usr/lib/python2.7/sre_parse.pyc'>,
 'stat': <module 'stat' from '/usr/lib/python2.7/stat.pyc'>,
 'sys': <module 'sys' (built-in)>,
 'sysconfig': <module 'sysconfig' from '/usr/lib/python2.7/sysconfig.pyc'>,
 'traceback': <module 'traceback' from '/usr/lib/python2.7/traceback.pyc'>,
 'types': <module 'types' from '/usr/lib/python2.7/types.pyc'>,
 'warnings': <module 'warnings' from '/usr/lib/python2.7/warnings.pyc'>,
 'zipimport': <module 'zipimport' (built-in)>}
"""