Lambda Functions

What You’ll Learn

You’ll learn how to write small, anonymous, one-line functions using the lambda keyword.

What is a Lambda Function?

A lambda function can take any number of arguments, but can only have one expression.

Syntax: lambda arguments : expression

# A regular function
def add_ten(a):
    return a + 10

# The same function as a lambda
add_ten_lambda = lambda a : a + 10

print(add_ten(5))        # 15
print(add_ten_lambda(5)) # 15

Multiple Arguments

multiply = lambda a, b : a * b
print(multiply(5, 6)) # 30

Why use Lambda Functions?

The power of lambda is better shown when you use them as an anonymous function inside another function, like built-in sorting or mapping methods.

points = [(1, 2), (5, 1), (3, 8)]

# Sort by the second item in each tuple
points.sort(key=lambda x: x[1])
print(points) # [(5, 1), (1, 2), (3, 8)]