On 09.08.16 00:59, Chris Angelico wrote:
class TooSimpleContextManager:
    """Now this time you've gone too far."""
    def __init__(self, func):
        self.func = func
    def __call__(self):
        self.gen = self.func()
        return self
    def __enter__(self):
        next(self.gen)
    def __exit__(self, type, value, traceback):
        try: next(self.gen)
        except StopIteration: pass
[...]
> My numbers are:
>
> 0.320 secs
> 1.354 secs
> slowdown: -4.23x
> 0.899 secs
> slowdown: -2.81x
> 0.831 secs
> slowdown: -2.60x
> 0.868 secs
> slowdown: -2.71x

I have got a slowdown 1.74x with TooSimpleContextManager with following implementation of __enter__ and __exit__:

    def __enter__(self):
        for res in self.gen:
            return res
        raise RuntimeError("generator didn't yield")
    def __exit__(self, type, value, traceback):
        for _ in self.gen:
            raise RuntimeError("generator didn't stop")


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