Understanding Python bytecode by implementing tail call optimization

This code does not do what the author thinks it does:

    def factorial(N, result=1):
        if N == 1:
            return 1
        return factorial(N-1, N*result)

No, but the time complexity is the same.

Okay but if you are going to call the function factorial, why not have it actually calculate a factorial? This would have done the job:

    def factorial(N, result=1):
        if N == 1:
            return result
        return factorial(N-1, N*result)

Assuming that you never call it with the result argument.

As written, it just looks like the author never ran the code.

Understanding Python bytecode by implementing tail call optimization (blog.fastforwardlabs.com)