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

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



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))


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))


[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))


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

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

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