Python Lambda Functions

What is a Lambda Function in Python?

A lambda function in Python is an anonymous function (a function without a name) used to write small and simple functions in a single line of code.

Syntax of Python Lambda Function:

lambda arguments: expression

• lambda is the keyword
• arguments can be one or more
• expression is the operation performed and returned

Example 1: Basic Lambda Function

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

Output:

25

Example 2: Lambda with Multiple Arguments

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

Output:

30

Use Lambda with Built-in Functions

Lambda with map()

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

Output:

[1, 4, 9, 16]

Lambda with filter()

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

Output:

[2, 4]

Lambda with sorted()

students = [("Alice", 88), ("Bob", 95), ("Charlie", 70)]
sorted_students = sorted(students, key=lambda x: x[1])
print(sorted_students)

Output:

[('Charlie', 70), ('Alice', 88), ('Bob', 95)]

Lambda vs def Function in Python

Limitations of Lambda Functions

• Only one expression allowed
• Cannot have statements (like loops, print, etc.)
• Not suitable for complex logic

Real-Life Use Case Example

Sorting Dictionary by Value

my_dict = {'a': 3, 'b': 1, 'c': 2}
sorted_dict = sorted(my_dict.items(), key=lambda item: item[1])
print(sorted_dict)

Output:

[('b', 1), ('c', 2), ('a', 3)]