Anonymous Functions

When you need to inline execute a small piece of code without defining a separate function, you can use anonymous functions. In Python, anonymous functions are called "lambda expressions" or "lambda functions".

Task

Using anonymous functions, map each item in a list of numbers to its square and print the new list.

JavaScript implementation

const numbers = [1, 2, 3, 4, 5];

const squaredNumbers = numbers.map(number => number ** 2);
console.log(squaredNumbers);

Python implementation

numbers = [1, 2, 3, 4, 5]

squared_numbers = list(map(lambda number: number ** 2, numbers))
print(squared_numbers)

Code Highlight

• Python uses the lambda keyword to create anonymous functions, while JavaScript uses function or => to create anonymous functions.
• Python's lambda functions cannot contain a function body, and the value of the expression is automatically returned as the return value. In contrast, anonymous functions in JavaScript can have function bodies and return statements.

Difference Quick View

Feature	JavaScript	Python
Creating Anonymous Functions	(params) => expression	lambda params: expression

tip

When a lambda function in Python has multiple parameters, separate each parameter with a ,.

Resources

• https://docs.python.org/3/tutorial/controlflow.html#lambda-expressions