Passing function as an argument in Python
A function can take multiple arguments, these arguments can be objects, variables(of same or different data types) and functions. Python functions are first class objects. In the example below, a function is assigned to a variable. This assignment doesn’t call the function. It takes the function object referenced by shout and creates a second name pointing to it, yell.
def shout(text):
return text.upper()
print (shout( 'Hello' ))
yell = shout
print (yell( 'Hello' ))
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Output:
HELLO
HELLO
Higher Order Functions
Because functions are objects we can pass them as arguments to other functions. Functions that can accept other functions as arguments are also called higher-order functions. In the example below, a function greet is created which takes a function as an argument.
def shout(text):
return text.upper()
def whisper(text):
return text.lower()
def greet(func):
greeting = func( "Hi, I am created by a function passed as an argument." )
print (greeting)
greet(shout)
greet(whisper)
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Output
HI, I AM CREATED BY A FUNCTION PASSED AS AN ARGUMENT.
hi, i am created by a function passed as an argument.
Wrapper function
Wrapper function or decorator allows us to wrap another function in order to extend the behavior of the wrapped function, without permanently modifying it. In Decorators, functions are taken as the argument into another function and then called inside the wrapper function. To know more about decorator click here.
Below is the example of a simple decorator.
def hello_decorator(func):
def inner1():
print ( "Hello, this is before function execution" )
func()
print ( "This is after function execution" )
return inner1
def function_to_be_used():
print ( "This is inside the function !!" )
function_to_be_used = hello_decorator(function_to_be_used)
function_to_be_used()
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Output:
Hello, this is before function execution
This is inside the function !!
This is after function execution
Lambda wrapper function
In Python, anonymous function means that a function is without a name. As we already know that def
keyword is used to define the normal functions and the lambda
keyword is used to create anonymous functions. This function can have any number of arguments but only one expression, which is evaluated and returned. Lambda function can also have another function as an argument. The below example shows a basic lambda function where another lambda function is passed as an argument.
square = lambda x:x * x
cube = lambda func:func * * 3
print ( "square of 2 is :" + str (square( 2 )))
print ( "\nThe cube of " + str (square( 2 )) + " is " + str (cube(square( 2 ))))
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Output:
square of 2 is :4
The cube of 4 is 64
Last Updated :
26 Aug, 2020
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