Python Closures

Before knowing the decorator concepts, its good to know about python closures

Closure conditions

To implement closures in python, below conditions should be matched

1. It should have a nested Function
2. Nested function should have a argument which pass from an enclosing(outer) function
3. Nested function should be called inside outer function

Nested function

Below is the best and simple example to understand the Nested Function and python closures. Nested function can access the enclosed function variable without global declaration

#Nested Function
def outer_function(name):
    def inner_function():
        print("The name is {}".format(name))
    inner_function()

outer_function("Rathna Schools")

Output

The name is Rathna Schools

Closure creation

Python closure stores the inner function state in a variable and call them whenever required like below

#Python Closures
def outer_function(name):
    def inner_function():
        print("The name is {}".format(name))
    return inner_function

result = outer_function("Rathna Schools")
#result variable behaves as independent inner function
result()

#Even though we deletes the outer function, closure variable survives in memory
del outer_function
result()

Output

The name is Rathna Schools
The name is Rathna Schools

When to use

Instead of using class for simple scenario, closure serves like better than class implementation like the below example

#Python Closures
def ten_multiples(input_num):
    def multiply():
        print(input_num*10)
    return multiply

result1 = ten_multiples(2)
result1()
result2 = ten_multiples(5)
result2()

Output

20
50

As mentioned at beginning, decorators are extremely leveraging the benefits of closures. It is explained in next tutorial with simple examples