# How to Use the Python lambda Function

09/07/2021

Contents

In this article, you will learn how to use the Python lambda function.

## Python lambda Function

The lambda function in Python is a small anonymous function that can take any number of arguments, but can only have one expression.

##### Syntax

The syntax for a lambda function is:

``lambda arguments : expression``
##### Examples
###### Example1

Here’s an example usage of the lambda function:

``````>>> add = lambda x, y : x + y
5
``````

In this example, lambda is defining an anonymous function (add) that takes two arguments (x and y) and returns their sum (x + y).

###### Example2

And lambda functions are often used in conjunction with higher-order functions, such as map, filter, and reduce, which take one or more functions as arguments and use them to process data.

Here’s an example using map:

``````>>> numbers = [1, 2, 3, 4, 5]
>>> squared = list(map(lambda x: x**2, numbers))
>>> print(squared)
[1, 4, 9, 16, 25]
``````

In this example, map takes two arguments: a lambda function and an iterable (numbers). The lambda function takes one argument (x) and returns its square (x**2). map applies this function to each element of the iterable, and the resulting list of squared values is stored in the variable squared.

###### Example3

The filter() function is used to filter out elements from an iterable based on some condition. Here’s an example:

``````>>> numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> evens = list(filter(lambda x: x % 2 == 0, numbers))
>>> print(evens)
[2, 4, 6, 8, 10]
``````

In this example, the filter() function takes two arguments: a lambda function and an iterable (numbers). The lambda function takes one argument (x) and returns True if x is even (x % 2 == 0), and False otherwise. filter applies this function to each element of the iterable and returns only the elements for which the function returns True.

###### Example4

Finally, the reduce() function is used to perform some operation on a list and reduce it to a single value. Here’s an example:

``````>>> from functools import reduce
>>> numbers = [1, 2, 3, 4, 5]
>>> product = reduce(lambda x, y: x * y, numbers)
>>> print(product)
120
``````

In this example, reduce takes two arguments: a lambda function and an iterable (numbers). The lambda function takes two arguments (x and y) and returns their product (x * y). reduce applies this function cumulatively to the elements of the iterable, and the final result is stored in the variable product.