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Unit 5 • Lesson 6

The Python Standard Library

Overview

Python's standard library includes built-in modules for everything from data compression to web requests. You'll explore how to discover available modules, read official documentation, and apply them to practical problems, unlocking powerful tools that come with Python.

Intermediate 25–30 min
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What You Will Learn in This Lesson

By the end of this lesson, you will know:

  • What the standard library is: Understand Python's extensive built-in module collection.
  • Exploring modules: Learn how to discover and explore available modules.
  • Reading documentation: Understand how to use help() and official docs.
  • Popular modules: Discover commonly used modules like datetime, json, csv, and os.

Why This Matters

Python comes with hundreds of modules already installed - you don't need to write code for common tasks! Whether you need to work with dates, parse JSON, read CSV files, or interact with the operating system, Python's standard library has you covered. Learning about the standard library saves you time and helps you write more powerful programs!

Step 1: What Is the Standard Library?

The Python standard library is a collection of modules that come with every Python installation. These modules are written in Python or C and provide ready-to-use functionality for common tasks:

Standard Library Modules
# All these modules come with Python - no installation needed!
import math          # Mathematical functions
import random        # Random number generation
import datetime      # Date and time handling
import json          # JSON data parsing
import csv           # CSV file handling
import os            # Operating system interface
import sys           # System-specific parameters
1

Pre-installed

Standard library modules come with Python - you don't need to install them separately. They're always available!

2

Well Documented

Every module has official documentation explaining what it does and how to use it. You can access it with help().

3

Reliable

These modules are maintained by Python's core developers and are thoroughly tested. They're production-ready!

Key Concept: The standard library is like a toolbox that comes with Python. Instead of building your own tools for common tasks, you can use the ones that are already included. This saves time and ensures your code is reliable!

Mini Practice #1: Exploring Standard Library

Try It Yourself

See what's available in the standard library:

Press Run to see output

What happened? Python's standard library includes hundreds of modules for tasks like math, random numbers, dates, file handling, and more. The sys module provides system-specific information like the Python version. All these modules are available without any installation!

Step 2: Popular Standard Library Modules

Here are some commonly used modules from the standard library:

datetime

Work with dates and times.

from datetime import datetime
now = datetime.now()

json

Parse and create JSON data.

import json
data = json.loads('{"key": "value"}')

csv

Read and write CSV files.

import csv
# Read CSV files easily

os

Interact with operating system.

import os
current_dir = os.getcwd()

collections

Specialized data structures.

from collections import Counter
counts = Counter([1, 2, 2, 3])

itertools

Functions for creating iterators.

import itertools
# Advanced iteration tools

Step 3: Discovering Modules

You can explore what modules are available using Python's built-in tools:

Finding Available Modules
# List all available modules
import sys
print(sys.modules.keys())

# Get help on a module
import math
help(math)

# See what's in a module
import random
print(dir(random))

Online Documentation

The official Python documentation (docs.python.org) has complete reference for all standard library modules. Each module has:

  • Purpose and introduction
  • Complete API reference
  • Usage examples
  • Best practices

Mini Practice #2: Using datetime Module

Try It Yourself

Try using the datetime module:

Press Run to see output

What happened? The datetime module provides powerful tools for working with dates and times. You can get the current time, format dates, calculate differences, and much more. This is all part of Python's standard library - no installation needed!

Step 4: Reading Documentation

You can access documentation right in Python:

Getting Help
# Get help on a module
import math
help(math)

# Get help on a specific function
help(math.sqrt)

# See module contents
print(dir(math))

Remember: The help() function shows documentation for modules, functions, and classes. If you're not sure how to use something, try help() first! For more detailed documentation, visit docs.python.org.

End-of-Lesson Exercises

Exercise 1: Use datetime Module

Import the datetime module and get the current date and time. Print it in a formatted string like "Current time: [date and time]".

Use from datetime import datetime, then datetime.now().

Write your code above and click "Check Answer" to verify it's correct.

Exercise 2: Explore Module Contents

Import the random module and use dir() to see what functions it contains. Then use help() to get information about the randint function. Print both results.

Use import random, then dir(random) and help(random.randint).

Write your code above and click "Check Answer" to verify it's correct.
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