19. Lambdas¶

Lambdas are one line functions. They are also known as anonymous functions in some other languages. You might want to use lambdas when you don’t want to use a function twice in a program. They are just like normal functions and even behave like them.

Blueprint

lambda argument: manipulate(argument)

Example

add = lambda x, y: x + y

print(add(3, 5))
# Output: 8

Here are a few useful use cases for lambdas and just a few ways in which they are used in the wild:

List sorting

a = [(1, 2), (4, 1), (9, 10), (13, -3)]
a.sort(key=lambda x: x[1])

print(a)
# Output: [(13, -3), (4, 1), (1, 2), (9, 10)]

Parallel sorting of lists

data = zip(list1, list2)
data = sorted(data)
list1, list2 = map(lambda t: list(t), zip(*data))