Python: List Modules, Search Path, Loaded Modules
List Available Modules
To list all modules, type pydoc modules
in terminal.
or in Python code:
print (help('modules') )
# python 3 # prints a list of existing modules print( help('modules'))

Note: in Ubuntu Linux, as of , 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)
.
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, thendir(__builtin__)
.
import re # print all names exported by the module print(dir(re)) # output # ['A', 'ASCII', 'DEBUG', 'DOTALL', 'I', 'IGNORECASE', 'L', 'LOCALE', 'M', 'MULTILINE', 'Match', 'Pattern', 'RegexFlag', 'S', 'Scanner', 'T', 'TEMPLATE', 'U', 'UNICODE', 'VERBOSE', 'X', '_MAXCACHE', '__all__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '__version__', '_cache', '_compile', '_compile_repl', '_expand', '_locale', '_pickle', '_special_chars_map', '_subx', 'compile', 'copyreg', 'enum', 'error', 'escape', 'findall', 'finditer', 'fullmatch', 'functools', 'match', 'purge', 'search', 'split', 'sre_compile', 'sre_parse', 'sub', 'subn', 'template']
Using Module
import module_name
- Load a module.
module_name.function_name
- Call a function in module.
# import the standard module named os import os # example of using a function # get current dir print(os.getcwd()) # /Users/xah/web/xahlee_info/python
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.
from os import getcwd # current dir print(getcwd())
Default “module”
All global (variable/function) names in Python are considered to be in the pseudo-module namespace named __main__
.
print(dir()) # ['__annotations__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__'] print(dir("__main__")) # ['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isascii', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', '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
.
import sys import pprint # pretty print module search paths pprint.pprint(sys.path) # ['/Users/xah/web/xahlee_info/python', # '/Users/xah/anaconda3/lib/python37.zip', # '/Users/xah/anaconda3/lib/python3.7', # '/Users/xah/anaconda3/lib/python3.7/lib-dynload', # '/Users/xah/anaconda3/lib/python3.7/site-packages', # '/Users/xah/anaconda3/lib/python3.7/site-packages/aeosa']
List Loaded Modules
Loaded module names is stored in the variable sys.modules
.
import sys import pprint # pretty print loaded modules pprint.pprint(sys.modules) # sample output # {'__main__': <module '__main__' from '/Users/xah/web/xahlee_info/python/xxtemp.20190318.38b.py3'>, # '_abc': <module '_abc' (built-in)>, # '_bootlocale': <module '_bootlocale' from '/Users/xah/anaconda3/lib/python3.7/_bootlocale.py'>, # '_codecs': <module '_codecs' (built-in)>, # ... # 'zipimport': <module 'zipimport' (built-in)>}