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Lambda Function (Anonymous Functions)

  • Learn how to create and use Lambda (anonymous) functions in Python.

  • What is a Lambda Function?

    A lambda function is a small, anonymous function (function without a name).

    👉 It can have any number of arguments, but only one expression.

    Why Do We Use Lambda Functions?

    Lambda functions are used to:

    •  Write short and simple functions

    • Reduce code length

    • Improve readability for small tasks

    •  Use functions only once

    • Work with map(), filter(), reduce()

    Real-Life Example:
     Sorting data, filtering values, quick calculations.

    Syntax of Lambda Function

    lambda arguments : expression

    Syntax Explanation

    Part

    Description

    lambda

    Keyword to define lambda

    arguments

    Input values

    :

    Separator

    expression

    Single line logic

    ⚠️ No return keyword is used.
     The result of the expression is returned automatically.

    Lambda vs Normal Function

    Feature

    Normal Function

    Lambda Function

    Name

    Has name

    Anonymous

    Code length

    Longer

    One line

    Expressions

    Multiple

    Single

    Use case

    Complex logic

    Small logic

Basic Lambda Function

This lambda function returns the square of a number. 

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

Lambda with Multiple Arguments

This lambda function adds two numbers. 

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

Direct Lambda Function Call

This lambda function is called directly without storing in a variable. 

print((lambda x: x + 10)(5))

Conditional Lambda Function

This lambda function checks whether a number is even or odd. 

check = lambda n: "Even" if n % 2 == 0 else "Odd"
print(check(7))

  • Lambda with map() Function

    What is map()?

    map() applies a function to each item of a list.

Using Lambda with map()

This program squares each number in the list. 

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

  • Lambda with filter() Function

    What is filter()?

    filter() selects items based on a condition.

Using Lambda with filter()

This program filters even numbers from the list. 

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

  • Lambda with reduce() Function

    What is reduce()?

    reduce() reduces a list to a single value.
     (It is available in the functools module.)

Using Lambda with reduce()

This program finds the sum of all elements in the list. 

from functools import reduce

numbers = [1, 2, 3, 4]
total = reduce(lambda a, b: a + b, numbers)
print(total)

  • Limitations of Lambda Functions

    • Only one expression

    • No statements (loops, try-except)

    • Less readable for complex logic

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