Lambda, map(), and filter()*

*What is a Lambda Function?*

A lambda function is an anonymous function written in one line using the lambda keyword.

✅ *Syntax:*

lambda arguments: expression

*Example:*

square = lambda x: x ** 2
print(square(5)) Output: 25

Use lambdas when you need a simple function for a short time — usually as an argument to map(), filter(), or sorted().




*map() — Apply a Function to All Items*

Takes a function and an iterable, and applies the function to every item in the iterable.


nums = [1, 2, 3, 4]
squares = list(map(lambda x: x ** 2, nums))
print(squares) Output: [1, 4, 9, 16]


*filter() — Filter Items Based on a Condition*

Filters the iterable by applying a function that returns True/False.


nums = [1, 2, 3, 4, 5, 6]
even = list(filter(lambda x: x % 2 == 0, nums))
print(even) Output: [2, 4, 6]


*Mini Project: Filter & Transform List*

nums = list(range(1, 21))

Step 1: Keep only even numbers
even_nums = list(filter(lambda x: x % 2 == 0, nums))

Step 2: Square the even numbers
squared_evens = list(map(lambda x: x ** 2, even_nums))

print(Even numbers:, even_nums)
print(Squared evens:, squared_evens)


You just combined filtering and transformation using lambda, map, and filter!