Lambda Functions and Modules in Python

Introduction

As your Python projects grow, it’s important to write clean and modular code.
Today you’ll learn two powerful concepts:

1. Lambda Functions – small, anonymous functions

2. Modules – reusable files containing Python code

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 1. What Is a Lambda Function?

A lambda function is a small anonymous function (a function without a name).
It is often used for short, simple operations where defining a full function isn’t necessary.

Syntax:

    lambda arguments: expression

Example:

    square = lambda x: x * x
    print(square(5))

Output:

    25

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2. Lambda with Multiple Arguments

    add = lambda a, b: a + b
   print(add(10, 20))

Output:

    30

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3. Using Lambda with Built-in Functions

Lambda is often used with map(), filter(), and reduce().

Example using map():

numbers = [1, 2, 3, 4, 5]
squares = list(map(lambda x: x**2, numbers))
print(squares)

Output:

[1, 4, 9, 16, 25]

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Example using filter():

nums = [10, 15, 20, 25, 30]
even = list(filter(lambda x: x % 2 == 0, nums))
print(even)

Output:

[10, 20, 30]

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4. What Is a Module?

A module is a Python file containing definitions of functions, variables, and classes.
Modules allow you to organize your code into separate files for reusability.

Example: Create a file mymodule.py

def greet(name):
    return f"Hello, {name}!"

Import and use it in another file:

import mymodule

print(mymodule.greet("Habbit2Code"))

Output:

Hello, Habbit2Code

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5. Importing Specific Items

You can import only what you need.

from math import sqrt
print(sqrt(16))

Output:

4.0

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6. Renaming a Module (Alias)

import math as m
print(m.pi)

Output:

3.141592653589793

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7. Built-in Modules

Python provides several useful built-in modules:

• math → mathematical operations

• datetime → date and time handling

• os → operating system interaction

• random → generate random numbers

Example:

import random
print(random.randint(1, 10))

Output:

7

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Why Use Modules?

•     Organize code into manageable pieces
•     Reuse existing code
•     Avoid redundancy
•     Improve readability

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Challenge for You

Create a module named calc.py containing functions for add, subtract, multiply, and divide.
Import it into another file and perform sample calculations.

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Final Thoughts

• Lambda functions make your code concise and functional.

• Modules make your code organized and reusable.

Together, they help you write clean, professional-quality Python programs.
In the next lesson, we’ll learn about File Handling in Python — reading and writing data to files.