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07. Closures and Nonlocal Variables

A closure is a function that "remembers" variables from its enclosing scope even after that scope is gone.

Example of a Closure​

def outer(msg):
    def inner():
        print(msg)
    return inner

hello = outer("Hello")
hello()

Nonlocal Variables​

def counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment

c = counter()
print(c())  # 1
print(c())  # 2

Practice Challenge​

Write a closure power_raiser(n) that returns a function raising numbers to the power of n.

Wrap-Up​

  • Closures capture variables from their enclosing scope.
  • Use nonlocal to modify outer-scope variables.