Closure

A closure is a function that retains access to its lexical scope, even if this function is executed from outside. The enclosed variables persist as long as the closure exist.

Example

def outer_function(x):
    def inner_function(y):
        return x + y
    return inner_function
    
closure = outer_function(10)
print(closure(5)) # Output: 15

Here, inner_function remember the value of x (10) even after outer_function has finish executing. ‡

NOTE

In this case, each function take one argument. It's also a case of currying