Lambda Functions

Sometimes you need a small function for a quick task.

Instead of writing a full function with def, Python gives a shorter way.

This is called a lambda function.

What Is a Lambda Function?

A lambda function is a small one-line function.

It is useful for simple actions.

Normal Function Example

def double(number):
    return number * 2

print(double(5))

Output

10

Same Example with Lambda

double = lambda number: number * 2

print(double(5))

Output

10

How It Works

lambda number: number * 2

Let’s break it down:

• lambda starts the function
• number is the input value
• : separates input from result
• number * 2 is the returned result

Why Use Lambda?

Use lambda when:

• The task is short
• You need a quick function
• You do not want a full def block

Another Example

add = lambda a, b: a + b

print(add(3, 7))

Output

10

With Sorted Data (Simple Example)

names = ["Tom", "Anna", "Mike"]

names.sort(key=lambda name: len(name))

print(names)

Output

['Tom', 'Mike', 'Anna']

The names are sorted by length.

When Not to Use Lambda

Do not use lambda for large or complex code.

Use normal functions when the logic needs many lines.

Code Along

square = lambda number: number * number

print(square(4))

Output

16

Mini Challenge

Build a quick multiply function.

Steps:

• Create a lambda function called multiply
• It should take two numbers
• Return the answer
• Print the result of 4 and 5

Expected output:

20

Real World Use Case

Programs use lambda functions for sorting, quick calculations, filtering data, and short helper tasks.

Quiz

1. What is a lambda function?
2. How many lines is it usually?
3. When should you use lambda?
4. Which keyword creates a lambda function?

Assignment

Create a lambda function called minus that subtracts two numbers and prints the result.

Summary

You learned that lambda functions are short one-line functions used for simple tasks and quick actions.