Overview of Useful Python Standard Library Modules with Example Code

cmd – provides a simple framework for building interactive command-line interpreters.

import cmd
class MyCmd(cmd.Cmd):
    def do_greet(self, line):
        print("Hello,", line)
    def do_exit(self, line):
        return True
MyCmd().cmdloop()

getpass – allows secure password input without echoing to the screen and also supports retrieving the current username.

import getpass
user = getpass.getuser()
password = getpass.getpass()
print(f"Username: {user}")

glob – finds file pathnames matching a specified pattern, similar to Unix shell pathname expansion.

import glob
files = glob.glob('*.txt')  # find all .txt files in the current directory
print(files)

pickle – implements serialization (pickling) and deserialization (unpickling) of Python object structures.

import pickle
data = {'key': 'value'}
with open('data.pkl', 'wb') as f:
    pickle.dump(data, f)  # serialize data to a file

shelve – offers a dictionary‑like persistent storage built on top of pickle.

import shelve
with shelve.open('mydata') as db:
    db['key'] = 'value'

codecs – provides support for encoding and decoding text files with various character encodings.

import codecs
with codecs.open('file.txt', 'r', encoding='utf-8') as file:
    content = file.read()

functools – supplies higher‑order functions such as decorators and partial function application; example shows an LRU‑cached recursive Fibonacci function.

from functools import lru_cache
@lru_cache(maxsize=None)
def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

inspect – offers utilities to retrieve information about live objects, such as obtaining source code of a function.

import inspect
def my_function():
    pass
print(inspect.getsource(my_function))  # get function source code

weakref – supports weak references to objects, helping with garbage collection and avoiding reference cycles.

import weakref
class MyClass:
    pass
obj = MyClass()
r = weakref.ref(obj)
print(r())  # prints the referenced object

xml.etree.ElementTree – enables parsing and creation of XML data structures.

import xml.etree.ElementTree as ET
tree = ET.parse('example.xml')
root = tree.getroot()
print(root.tag)