TB, what's your use case for passing a float to a semaphore? Semaphores are conceptually tied to integers. You've kept arguing a few times now that the workaround you need are clumsy, but you've not explained why you're passing floats in the first place. A "fractional resource" just doesn't sound like a real use case to me.
On Mon, Jan 30, 2012 at 10:40 AM, T.B. <bauerto...@gmail.com> wrote: > > On 2012-01-30 01:46, Victor Stinner wrote: >>> >>> >>> But why would you want to pass a float? It seems like API abuse to me. >> >> >> If something should be changed, Semaphore(arg) should raise a >> TypeError if arg is not an integer. >> > Short version: > I propose the the change to be > > - while self._value == 0: > + while self._value < 1: > This should not change the flow when Semaphore._value is an int. > > Longer explanation: > I thought it is surprising to use math.floor() for threading.Semaphore, but > now as you propose, we will need to use something like > int(math.floor(value)) in Python2.x - which is even more surprising. That is > because math.floor() (and round() for that matter) return a float object in > Python2.x. > > Note: isinstance(4.0, numbers.Integral) is False, even in Python3.x, but > until now 4.0 was valid as a value for Semaphore(). Also, using the builtin > int()/math.trunc() on a float is probably not what you want here, but rather > math.floor(). > > The value argument given to threading.Semaphore() is really a duck (or an > object) that can be compared to 0 and 1, incremented by 1 and decremented by > 1. These are properties that fit float. Why should you force the entire > builtin int behavior on that object? > > I agree that using a float as the counter smells bad, but at times you might > have something like a fractional resource (which is different from a > floating point number). In such cases Semaphore.acquire(), after the tiny > patch above, can be thought as checking if you have at least one "unit of > resource" available. If you do have at least one such resource - acquire it. > This will make sure the invariant "The counter can never go below zero" > holds. > > Regards, > TB > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/guido%40python.org -- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
