Writing Anonymous function in Python

Writing Anonymous function in Python

Victory Chiamaka Wekwa's photo
Victory Chiamaka Wekwa
·Jul 22, 2020·

2 min read

In this article, I will be writing about the anonymous functions also called the lambda function, their syntax and how to use them with examples.

What are Anonymous function in Python

Anonymous function are functions that is defined without a name. They allow single line functions to be written that might be used once or given a name to be used multiple times.

How to use Anonymous function in Python.

Anonymous function is defined as:

name = lambda argument (s) : expression

They can have many parameters but they can only have one argument. The expression is the one evaluated and then the result returned.

Example of Anonymous function

To write a function to multiply two numbers 2 and 3.

Using the expression:

name = lambda argument(s) : expression


Define a name

Assign arguments to the lambda function

Input the expression

Print out the result

To solve the example we have;

mult = lambda x,y:x*y




In the example above,

mult is the name (identifier).

x,y are arguments.

x*y is the expression to be evaluated for result to be returned.

Anonymous function allows a function to be called immediately.

Usage with built-in function

Anonymous function can be used with built-in function like filter() and map().

Using Anonymous function with Filter()

In using filter(), it takes in a list and a function as an argument. It provides an effective way to filter out all the elements in a list. When the function is called, it returns a new list which contains all the items for which the function evaluates to True.

Example: Using filter() to find, remove and print out all the even numbers in a list.

my_numbers =[1,4,6,2,8,20,22,3,5,7,9,80]
even_numbers = list(filter(lambda x:(x%2==0),my_numbers)




Using the Anonymous function with map()

In using the map(), it accepts a function and a list as it's argument. When it is called, it returns a new list which contains all the items for which the function evaluates but for each item.

Example: Using an Anonymous function to find the square of a number.

numbers = [1, 4,6,8,9,5,12,18]
square = list(map(lambda x: x**2, numbers))




Finally, anonymous function can either be used independently as seen in the examples above or inside other functions.

I hope you enjoyed reading this, kindly leave a comment or like this article.

Thank you

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