Tell about closures in Python. How does a function inside a function use variables from the outer function?

In Python, a closure is a function that remembers and can use variables from the scope of the outer function even after the outer function has finished executing.

When a function is defined inside another function, the inner function can access the variables of the outer function. These variables are stored in a special object called a closure.

Example:

def outer(x):
    y = 10
    def inner(z):
        return x + y + z  # Uses variables from the outer function
    return inner

f = outer(5)
print(f(3))  # Outputs 18 (5 + 10 + 3)

Here, inner is a closure that 'captures' the variables x and y from outer. Even after outer has returned inner, these variables remain accessible inside inner.