global — Intermediate Playground

Declares a variable inside a function as belonging to the global scope

Python Playground

# Problem: global state makes code hard to test and debug
counter = 0

def bad_increment():
    global counter
    counter += 1
    return counter

# Better: use a class
class Counter:
    def __init__(self):
        self.value = 0
    def increment(self):
        self.value += 1
        return self.value

c = Counter()
print(c.increment())
print(c.increment())
print(c.increment())

# Or use a closure
def make_counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment

inc = make_counter()
print(inc())
print(inc())

Output

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Classes and closures are almost always better than global variables. They allow multiple independent instances and are easier to test.

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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