What is the Anonymous function in Python?
Introduction:
Lambda functions are single-line functions that can take multiple arguments but have a single expression and return value.
There are three main components of the lambda function:
- keyword: lambda
- arguments before the colon
- expression/return statements after colon
Lambda
- In several programming languages, anonymous functions are introduced using the lambda keyword and anonymous functions are often referred to as lambdas or lambda abstractions.
- Anonymous functions have been a feature of programming languages since Lisp in 1958. A growing number of modern programming languages now support anonymous functions.
- A lambda function is a small anonymous function.
- A lambda function can take any number of arguments, but can only have one expression. The expression is evaluated and returned.
- Lambda functions can be used wherever function objects are required.
- Lambda function uses the keyword
lambda
Syntax:
lambda arguments: expression
Example:
Add 20 to an argument (a) and return the results:
x = lambda a:a+20print(x(5))
Lambda functions can take any number of arguments:
Example 1:
Multiply argument x with argument y and return the result:
s = lambda x, y : x * yprint(s(3, 4))
Example 2:
Add the argument a,b, and c and return the result:
x = lambda a, b, c : a + b + cprint(x(3, 7, 9))
Use of Lambda Function in Python
The lambda function is commonly used with the Python built-in functions filter() and map().
Lambda with filter()
The Python built-in filter() function accepts a function and a list as an argument. It provides an effective way to filter out all the elements of the sequence and returns the new sequence whose function evaluates to True.
Example:
lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]lst1 = list(filter(lambda x:(x % 2 == 0), lst))print(lst1)
Lambda with map()
The map() function in Python accepts a function and a list. It gives a new list that contains all modified items returned by the function for each item.
Example:
lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]lst1 = list(map(lambda x:x * 2, lst))print(lst1)
