LAMBDA FUNCTION IN PYTHON

Python Free Tutorial

Lambda function in python is an anonymous function that takes any number of arguments but takes only one expression. An anonymous function is a function defined without a name.

SYNTAX
lambda arguments: expression

Normal functions are defined using the def keyword whereas anonymous functions are defined using the lambda keyword.

EXAMPLE 01: To add two numbers
>>> x = lambda a, b : a + b
>>> print(x(3,4))
 
Output:
7
EXAMPLE 02: To multiply three numbers
>>> x = lambda a, b : a * b * c
>>> print(x(3,4,2))
 
Output:
24

WHY LAMBDA FUNCTION ??

Lambda function in python is used when we need a nameless function for a short period of time. We generally use lambda function inside another function. Let’s take an example:

>>> def normal_function(n):
              return lambda a : a + n
>>> callfn = normal_function(2)
>>> print(callfn(5))

Output: 7

Lambda functions can be used together with Python’s built-in functions like map( ), filter( ), reduce( ), etc.

LAMBDA WITH FILTER( )

The filter() function takes a lambda function together with a list as the arguments. This function can be used to filter out all the elements of the list which satisfies the condition and returns a new list.

# filter() with lambda()
# create list of number divisible by 3
>>> list_01 = [1,2,3,4,5,6,7,8,9,10]
>>> new_list = list(filter(lambda x: (x%3 == 0) , list_01))
>>> print(new_list)
 
Output:
[3,6,9]
LAMBDA WITH MAP( )

The map() function takes a function together with a list as the argument. This function can be used to generate elements of a list returned by that function for each item.

>>> original_list = [2,4,6,8,10,12,14,16]
>>> new_list = list(map(lambda x: x * 2 , original_list))
>>> print(new_list)
 
Output:
[1,3,5,7,9,11,13,15]
LAMBDA WITH REDUCE( )

The reduce() function takes a function together with a list as the argument. We obtain a reduced output using this function. This is a part of functools module. Let’s take a look at an example:

>>> from functools import reduce
>>> old = [1,2,3,4,5,6,7,8,9,10]
>>> sum = reduce((lambda x, y: x + y), old)
>>> print (‘Sum of the first ten natural number is :’,sum)
 
Output:
Sum of the first ten natural number is 55

Process involved = (((((((((1+2)+3)+4)+5)+6)+7)+8)+9)+10) = 55. Follow us on instagram for more contents.

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5 Comments on “LAMBDA FUNCTION IN PYTHON”

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