Lambdas in Python

In Python, anonymous functions like arrow-functions in JavaScript (() => {}) are immediately invoked and unnamed. They are called lambdas.

Whilst they are unnamed, just like JS, the value they return can be stored in a variable. They do not require the return keyword.

They are most often used unnamed with the functional methods map, filter and reduce.

Here is the two syntaxes side by side:

// JavaScript

const double = (x) => x * x;

# Python

double = lambda x: x * x

Here is a lambda with multiple parameters:

func = lambda x, y, z: x + y + z
print(func(2, 3, 4))
# 9

Lambdas obviously enshrine functional programming paradigms. Therefore they should be pure functions, not mutating values or issueing side effects. For example, it would be improper (though syntactically well-formed) to use a lambda to print something