Python 3.0+Functionsterm

global / nonlocal

scope

global declares a variable from the global namespace. nonlocal — one from an enclosing function (not the global scope).

Syntax

global x
nonlocal y

You only need these to rebind: reading a global, or mutating a mutable object in place (list.append), works without global. nonlocal requires the variable to already exist in an enclosing function — it can't create a new one and won't reach the global scope.

Examples

counter = 0
def increment():
    global counter
    counter += 1
increment()
print(counter)  # → 1

def make_counter():
    count = 0
    def inc():
        nonlocal count
        count += 1
        return count
    return inc
c = make_counter()
print(c(), c(), c())  # → 1 2 3
total = 0
def add(x):
    global total
    total += x
add(5); add(3)
print(total)  # → 8

def outer():
    x = 0
    def middle():
        nonlocal x
        x = 10
        def inner():
            nonlocal x
            x += 1
        inner()
    middle()
    return x
print(outer())  # → 11

# global можно объявить несколько переменных
a = b = 0

def reset():
    global a, b
    a = b = 1
reset()
print(a, b)  # → 1 1

def acc():
    s = 0
    def add(n):
        nonlocal s
        s += n
        return s
    return add
f = acc()
print(f(3), f(4))  # → 3 7

See also

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