How to count function calls using decorators?

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I'm refreshing my memory about some python features that I didn't get yet, I'm learning from this python tutorial and there's an example that I don't fully understand. It's about a decorator counting calls to a function, here's the code:

def call_counter(func):
    def helper(x):
        helper.calls += 1
        return func(x)
    helper.calls = 0
    return helper

@call_counter
def succ(x):
    return x + 1

if __name__ == '__main__':
    print(succ.calls)
    for i in range(10):
        print(succ(i))
    print(succ.calls)

What I don't get here is why do we increment the calls of the function wrapper (helper.calls += 1) instead of the function calls itself, and why does it actually working?

python-decorators python
5 Answers

Example with Class Decorator

When you decorate a function with the Class Decorator, every function has its own call_count. This is simplicity of OOP. Every time CallCountDecorator object is called, it will increase its own call_count attribute and print it.

class CallCountDecorator:
    """
    A decorator that will count and print how many times the decorated function was called
    """

    def __init__(self, inline_func):
        self.call_count = 0
        self.inline_func = inline_func

    def __call__(self, *args, **kwargs):
        self.call_count += 1
        self._print_call_count()
        return self.inline_func(*args, **kwargs)

    def _print_call_count(self):
        print(f"The {self.inline_func.__name__} called {self.call_count} times")


@CallCountDecorator
def function():
    pass


@CallCountDecorator
def function2(a, b):
    pass


if __name__ == "__main__":
    function()
    function2(1, b=2)
    function()
    function2(a=2, b=3)
    function2(0, 1)

# OUTPUT
# --------------
# The function called 1 times
# The function2 called 1 times
# The function called 2 times
# The function2 called 2 times
# The function2 called 3 times
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