CIT PYTHON COHORT THREE
  • CIT Python Cloud Software Engineering
  • week one
    • What is Python
    • Python Syntax
    • variables
    • Numbers / Integers
  • week Two
    • Control Flow Statements
      • If Statements
      • For Loops
      • While Loops
      • Break and Continue Statements
    • Operators
      • Assignment Operators
      • Arithmetic Operators
      • Comparison Operators
      • Logical Operators
      • Bitwise Operators
      • Identity Operators
      • Membership Operators
    • Data Types
      • Strings
      • Numbers
      • Booleans
      • Lists
      • Dictionaries
      • Tuples
      • Sets
  • Week 3
    • Functions
      • Function Arguments
      • Python Recursion
      • Python Anonymous/Lambda Function
    • Object Oriented Programming
      • Classes
      • Inheritance
      • Polymorphism
      • Abstraction
      • Encapsulation
    • Python Modules
      • Python Packages
      • Python Built-in Modules
      • Python Standard Library
      • Python Third Party Modules
    • Python Exceptions
      • Python Try Except
      • Python Raise
      • Python Assert
      • Python User-defined Exceptions
  • Week 4 - File Handling
  • Week6
    • Data Structures and Algorithms
      • DSA Introduction
      • What is an Algorithm?
      • Data Structures and Types
      • Stack
      • Queue
      • Linked List
      • Bubble Sort Algorithm
      • Selection Sort Algorithm
      • Insertion Sort Algorithm
      • Merge Sort Algorithm
      • Quick Sort Algorithm
  • Week8
    • Cryptography
      • Reverse Cipher
      • Caesar Cipher
      • Hash Functions
        • Applications of Hash Functions
        • Examples of Hash Functions
  • Assignments and Solutions
    • Loops
Powered by GitBook
On this page

Was this helpful?

Edit on GitHub
  1. Week 3
  2. Functions

Python Anonymous/Lambda Function

What are lambda functions in Python?

In Python, an 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.

Syntax of Lambda Function in python

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

Here is an example of lambda function that doubles the input value.

# 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.

Example use with filter()

The filter() function in Python takes in a function and a list as arguments.

The function is called with all the items in the list and a new list is returned which contains items for which the function evaluates to True.

Here is an example use of filter() function to filter out only even numbers from a list.

# Program to filter out only the even items from a list
my_list = [1, 5, 4, 6, 8, 11, 3, 12]

new_list = list(filter(lambda x: (x%2 == 0) , my_list))

print(new_list)

Output

[4, 6, 8, 12]

Example use with map()

The map() function in Python takes in a function and a list.

The function is called with all the items in the list and a new list is returned which contains items returned by that function for each item.

Here is an example use of map() function to double all the items in a list.

# Program to double each item in a list using map()

my_list = [1, 5, 4, 6, 8, 11, 3, 12]

new_list = list(map(lambda x: x * 2 , my_list))

print(new_list)

Output

[2, 10, 8, 12, 16, 22, 6, 24]
PreviousPython RecursionNextObject Oriented Programming

Last updated 2 years ago

Was this helpful?