How to create higher-order functions in Python?

In Python, a function that takes another function as a parameter or returns a function as output is called a higher-order function. Let's take a look at its features -

• This function can be stored in a variable.

• This function can be passed as a parameter to another function.

• Higher-order functions can be stored in lists, hash tables, etc.

• Functions can be returned from functions.

Let’s look at some examples −

Function as Object

Example

Example

In this example, these functions are treated as objects. Here, the function demo() is assigned to a variable -

# Creating a function
def demo(mystr):
   return mystr.swapcase() # swapping the case

print(demo('Thisisit!'))
sample = demo
print(sample('Hello'))

Output

tHISISIT!
hELLO

Passing functions as parameters

Example

Example

Passed as a parameter in this function. demo3() The function calls the demo() and demo2() functions as parameters.

def demo(text):
   return text.swapcase()

def demo2(text):
   return text.capitalize()

def demo3(func):
   res = func("This is it!") # Function passed as an argument
   print (res)

# Calling
demo3(demo)
demo3(demo2)

Output

tHIS IS IT!
This is it!

Now, let’s discuss decorators. We can use decorators as higher order functions.

Decorators in Python

Example

Example

In a decorator, a function is passed as a parameter to another function and then called in the wrapping function. Let’s look at a quick example −

@mydecorator
def hello_decorator():
   print("This is sample text.")

The above can also be written as -

def demo_decorator():
   print("This is sample text.")
hello_decorator = mydecorator (demo_decorator)

Decorator example

Example

Example

In this example, we will work with decorators as higher-order functions -

def demoFunc(x,y):
   print("Sum = ",x+y)

# outer function
def outerFunc(sample):
   def innerFunc(x,y): # inner function
      return sample(x,y)
   return innerFunc

# calling
demoFunc2 = outerFunc(demoFunc)
demoFunc2(10, 20)

Output

Sum = 30

Example

Example

def demoFunc(x,y):
   print("Sum = ",x+y)

# outer function
def outerFunc(sample):
   def innerFunc(x,y): # inner function
      return sample(x,y)
   return innerFunc

# calling
demoFunc2 = outerFunc(demoFunc)
demoFunc2(10, 20)

Output

Sum = 30

Apply syntax decorator

Example

Example

The above example can be simplified using a decorator with @symbol. The application of decorators can be simplified by placing the @ symbol before the function we want to decorate -

# outer function
def outerFunc(sample):
   def innerFunc(x,y): # inner function
      return sample(x,y)
   return innerFunc

@outerFunc
def demoFunc(x,y):
   print("Sum = ",x+y)

demoFunc(10,20)

Output

Sum = 30

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