🪟 Closures

A closure is a function that remembers the variables from its outer (enclosing) scope, even after that outer function has finished executing.

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✅ Why Closures Matter

• Let you create customized functions (function factories)
• Hide internal state without classes
• Enable patterns like decorators

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✅ Example: Function Factory

def make_adder(n):
    def add(x):
        return x + n
    return add

add5 = make_adder(5)
add5(10)  # 15

Here, add remembers the value of n even after make_adder returns.

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✅ Using nonlocal

To update an outer variable, use nonlocal.

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

next_count = counter()
next_count()  # 1
next_count()  # 2

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🔍 Key Takeaways

• Closures capture values from enclosing scopes.
• They are useful for customization and encapsulation.
• nonlocal lets you update captured variables.

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Next: Decorators