Standard Library Overview

Python’s standard library is a collection of modules and packages that come pre-installed with Python. It provides a wealth of functionality, enabling developers to perform a variety of tasks without installing external packages.

Categories of Modules

1. File and Directory Management

• os: Interact with the operating system.
• shutil: High-level file operations.
• glob: Find files by patterns.

Examples:

import os

print(os.getcwd())  # Get current working directory
os.mkdir("new_folder")  # Create a new directory

2. Data and Time Handling

• datetime: Work with dates and times.
• time: Time-related functions.
• calendar: Generate and manipulate calendars.

Examples:

from datetime import datetime

now = datetime.now()
print(now)  # Output: Current date and time

3. Mathematics

• math: Mathematical functions.
• random: Generate random numbers.
• statistics: Statistical functions.

Examples:

import math

print(math.sqrt(16))  # Output: 4.0

4. String Handling

• string: Constants and utility functions for strings.
• re: Regular expressions for advanced string processing.

Examples:

import re

pattern = r"\d+"
match = re.search(pattern, "There are 123 apples")
print(match.group())  # Output: 123

5. Internet and Web Services

• urllib: Work with URLs.
• http.client: HTTP protocol client.
• json: Parse and generate JSON data.

Examples:

import json

data = {"name": "Alice", "age": 30}
json_data = json.dumps(data)
print(json_data)  # Output: {"name": "Alice", "age": 30}

6. System Utilities

• sys: System-specific parameters and functions.
• argparse: Command-line argument parsing.
• logging: Logging utility.

Examples:

import sys

print(sys.version)  # Python version

7. Concurrency and Parallelism

• threading: Thread-based parallelism.
• multiprocessing: Process-based parallelism.

Examples:

import threading

def worker():
    print("Thread is running")

thread = threading.Thread(target=worker)
thread.start()

8. Data Persistence

• pickle: Serialize and deserialize Python objects.
• shelve: Persistent, dictionary-like objects.

Examples:

import pickle

data = {"name": "Alice", "age": 30}
with open("data.pkl", "wb") as file:
    pickle.dump(data, file)

9. Testing and Debugging

• unittest: Unit testing framework.
• pdb: Python debugger.

Examples:

import unittest

class TestExample(unittest.TestCase):
    def test_addition(self):
        self.assertEqual(1 + 1, 2)

unittest.main()

10. Compression and Archiving

• zipfile: Work with ZIP files.
• tarfile: Work with TAR files.

Examples:

import zipfile

with zipfile.ZipFile("example.zip", "r") as zip_ref:
    zip_ref.extractall("output_folder")

11. Email and Communication

• smtplib: Send emails using SMTP.
• email: Create and parse email messages.

Examples:

import smtplib

# Connect to SMTP server
server = smtplib.SMTP("smtp.example.com", 587)
server.starttls()
server.login("user@example.com", "password")
server.quit()

12. Development Tools

• abc: Abstract base classes.
• inspect: Inspect live objects.

Examples:

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        pass

Benefits of Using the Standard Library

1. No Installation Required: Comes with Python by default.
2. Reliable and Well-Maintained: Built and maintained by Python developers.
3. Cross-Platform: Works across operating systems.

Practice Exercises

1. File Management:
   • Use the os and shutil modules to create a directory, move a file into it, and then delete the directory.
2. Data Handling:
   • Write a script that uses json to read a JSON file and print its contents.
3. String Processing:
   • Use the re module to find all numbers in a given string.
4. Datetime:
   • Create a script that calculates the number of days until the next year using datetime.
5. Testing:
   • Write a simple unit test using the unittest module.

Python’s standard library provides all the tools you need to perform common programming tasks effectively and efficiently.