Can you explain what a closure is and how it functions in the Python language?

In Python, a closure is a function that remembers and can use variables from the scope in which it was created, even if that scope is no longer active.

Example:

def outer():
    x = 10
    def inner():
        return x + 5
    return inner

func = outer()
print(func())  # Outputs 15

Here, inner is a closure that "closes over" the variable x from the outer function outer. Even after outer has finished executing, inner retains access to x.

This is useful for creating functions with preserved state without using global variables.