nonlocal — Expert Playground

Declares a variable inside a nested function as belonging to the enclosing scope

Python Playground

import dis

def outer():
    x = 10
    def inner():
        nonlocal x
        x += 1
        return x
    return inner

print("outer bytecode:")
dis.dis(outer)
print("\ninner bytecode:")
dis.dis(outer())

# outer stores x as a cell variable (LOAD_DEREF/STORE_DEREF)
# inner accesses x as a free variable (also LOAD_DEREF/STORE_DEREF)
# Both use the same cell object, enabling shared state

fn = outer()
print(f"\nFree vars: {fn.__code__.co_freevars}")
print(f"Closure: {fn.__closure__}")
print(f"Cell contents: {fn.__closure__[0].cell_contents}")

Output

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nonlocal variables use cell objects shared between the enclosing and inner function. Both access the cell via LOAD_DEREF/STORE_DEREF opcodes. The cell is stored in __closure__.

Challenge

Try modifying the code above to explore different behaviors. Can you extend the example to handle a new use case?

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