Lambda Functions

Anonymous Functions

Sometimes you need a small function for a short period of time, and you don’t even want to give it a name using def. These are called Anonymous Functions, and in Python, we create them using the lambda keyword.

The Lambda Syntax

The syntax for a lambda function is: lambda arguments : expression

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

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

print(add_ten(5))
print(add_ten_lambda(5))

Characteristics:

1. It can take any number of arguments.
2. It can only have one expression.
3. It automatically returns the result of that expression.

Why use Lambda?

Lambdas are most useful when passed as an argument to another function.

Example: Custom Sorting

Imagine you have a list of tuples representing students and their scores, and you want to sort them by score.

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students = [("Alice", 85), ("Bob", 75), ("Charlie", 95)]

# Sort by the second item in each tuple (the score)
students.sort(key=lambda student: student[1])

print(students)

Lambda vs. Def

Interactive Practice

Try writing a lambda function that takes one number and returns its square (number multiplied by itself).