# What is a lambda function in Python?

This post is lesson 18 of 54 in the subject Python Programming Language

## 1. What is a lambda function?

A lambda function in Python is an anonymous function, meaning it is a function without a name. In Python, we use the keyword ‘lambda‘ to define a lambda function. The syntax for a lambda function is as follows:

``lambda arguments: expression``

Lambda functions can have any number of parameters but only one expression. The expression is calculated, evaluated, and then returned. An example of a lambda function is as follows:

``````# lambda function
double = lambda x: x * 2
print(double(5))

x ="Gochocit.com"
# lambda function gets pass to print
y = lambda x : print(x)
y(x)``````

#### Result:

``````10
Gochocit.com``````

## 2. Using Lambda Function in Python

A lambda function often uses in another function to help perform a task. Lambda functions are also often used as arguments for other functions such as `filter()`, `map()`, etc.

### Lambda Function is Often Inside a Function

``````def power(n):
return lambda a : a ** n

# set n = 2
# base = lambda a : a**2
# returned to base
base = power(2)
print("8 powerof 2 = ", base(8))

base = power(5)
print("8 powerof 5 = ", base(8))``````

#### Result:

``````8 powerof 2 =  64
8 powerof 5 =  32768``````

### Using lambda Function with filter() Function

The `filter()` function in Python takes a function and a list as arguments. The `filter()` function iterates through all the items in the list and filters out the items that satisfy a particular condition.

``````# numbers list
numbers = [1, 5, 4, 6, 8, 11, 3, 12]
# filter out only the even items from numbers list
new_numbers = list(filter(lambda x: (x%2 == 0) , numbers))
print(new_numbers)``````

#### Result:

``[4, 6, 8, 12]``

In the above example, the `filter()` function helps to filter out even numbers from a list.

### Using Lambda Function with map() Function

The `map()` function in Python takes a function and a list as arguments. The `map()` function iterates through each item in the list. While iterating, the `map()` function performs calculations on each item using the function argument and returns a new list with the calculated items.

``````# numbers list
numbers = [1, 5, 4, 6, 8, 11, 3, 12]
# double each item in numbers list using map()
new_numbers = list(map(lambda x: x * 2 , numbers))
print(new_numbers)``````

#### Result:

``[2, 10, 8, 12, 16, 22, 6, 24]``

In the above example, the `map()` function helps to double all the items in a list.

5/5 - (1 vote)
Previous and next lesson in subject<< How to Create a Recursive Function in Python?Guide to using decorators in Python >>
0 Shares