Sometimes you may need to define small one-action function. Especially it's quite useful for preprocessing data. In this case, you can use `lambda` function.

Lambda function is a small anonymous function (unless you assign it to some variable) that can have many arguments, but only one expression/instruction. To define lambda function use the keyword `lambda` followed by arguments. Next, set the colon sign, and define the instruction. For example, the `circle_area` function can be expressed as lambda:

# Import the library
import math

# Define lambda function
area = lambda R: print("Area:", math.pi*R**2)

# Calling function
area(5)
area(8)

Lambda Functions