Python : Anonymous/Lambda Functions

Hi all,

Today we are going to discuss about lambda or anonymous function in Python. So let’s explore the lambda.

Lambda in Python

A lambda is a anonymous function which can take any number of arguments but unlike normal functions it can evaluate or return function in only in one expression. It works like def function but can take arguments in only one expression.

Syntax:

lambda arguments : expression

In Python, a lambda function is a special type of function without the function name. For example,

lambda : print('Hello World')

Here, we have created a lambda function which do not gives error

Before exploring more about lambda it’s necessary to know about Python Functions

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Using lambda

Add argument num1 and num2 and get the result

# Adding arguments num1 and num2
Addition = lambda  num1, num2 : num1 + num2

# Giving values to add 
print(Addition(7, 9))
-------------------------------------------------
Output
16

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Multiplying num1 argument with num2 argument and get the result

Multiplication = lambda  num1, num2 : num1 * num2 
print(Multiplication(7, 9))
----------------------------------------------------------
Output
63

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Summarize arguments num1, num2, num3, num4 and get the result

# We will give four arguments : num1, num2, num3, num4
Addition = lambda  num1, num2, num3, num4 : num1 + num2 + num3 + num4

# We will give four values to add
print(Addition(7, 9, 6, 3))
-------------------------------------------------------------------
Output
25

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Uses of lambda function

• Supports single line statements that returns some value.
• Using lambda function can sometime improves the readability of code
• Good for performing short operations/data manipulation

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We will use the lambda function with list comprehension

Multiply_numbers = [lambda arg = num1: arg * 9 for num1 in range(1, 11)]

# iterate on each lambda function
for item in Multiply_numbers:
    print(item())
-------------------------------------------------------------------
Output
9
18
27
39
45
54
63
72
81
90

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We will filter the list of peoples who’s age is more than 18 years using lambda function and filter function

age_people = [7,8,88,75,89,90,5,43,17]

adults = list(filter(lambda age: age > 18, age_people))
print(adults)

------------------------------------------------------------
[88, 75, 89, 90, 43]

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Filter all the even numbers from the list

numbers = [75,76,89,87,91,90,767,54]

odd_numbers = list(filter(lambda num:(num%2!=0), numbers))
print(odd_numbers)

-----------------------------------------------------------
Output
[75, 89, 87, 91, 767]

We have very good series of Python articles, please have a look – https://knowledge-junction.in/category/python/

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