Python:Lambda Expressions, Map, and Filter

Lambda Expressions, Map, and Filter

What are lambda functions in Python?

In Python, anonymous function is a function that is defined without a name.

While normal functions are defined using the def keyword, in Python anonymous functions are defined using the lambda keyword.

Hence, anonymous functions are also called lambda functions.

How to use lambda Functions in Python?

A lambda function in python has the following syntax.

lambda arguments: expression

Lambda functions can have any number of arguments but only one expression. The expression is evaluated and returned. Lambda functions can be used wherever function objects are required.

Example of Lambda Function in python

# Program to show the use of lambda functions

double = lambda x: x * 2

print(double(5))

# Output: 10

In the above program, lambda x: x * 2 is the lambda function. Here x is the argument and x * 2 is the expression that gets evaluated and returned.

This function has no name. It returns a function object which is assigned to the identifier double. We can now call it as a normal function. The statement

double = lambda x: x * 2

is nearly the same as

def double(x):

   return x * 2

Use of Lambda Function in python

We use lambda functions when we require a nameless function for a short period of time.

In Python, we generally use it as an argument to a higher-order function (a function that takes in other functions as arguments). Lambda functions are used along with built-in functions like filter(), map() etc.

There are two built in functions, filter and map. Once we know about how these operate, we can learn about the lambda expression, which will come in handy.