Global and Nonlocal

By default, assignment inside a function creates a local variable. The global and nonlocal keywords let a function explicitly modify a variable defined in an outer scope — global targets the module-level scope, while nonlocal targets the nearest enclosing function scope.

global Keyword

Modifying a Global Variable

x = 10

def function():
    global x
    x = 20

function()
print(x)  # 20

nonlocal Keyword

Modifying an Enclosing Variable

def outer():
    x = 10

    def inner():
        nonlocal x
        x = 20

    inner()
    print(x)  # 20

Summary

• global: modifies a variable at module level
• nonlocal: modifies a variable in the enclosing function scope
• Both allow a function to modify variables defined in an outer scope