On Tue, Jun 26, 2018, 11:43 PM Jacco van Dorp <j.van.d...@deonet.nl> wrote:
> 2018-06-26 17:34 GMT+02:00 Franklin? Lee <leewangzhong+pyt...@gmail.com>: > > Caller detects: The caller checks length before calling the dunder. If > there > > is no dunder, it doesn't check. Are there real-world cases where length > is > > not defined on an iterable collection? > > Generators dont have a __len__ method. And they might have min/max > that can be calculated without iterating over the entire thing. The > builtin range() is an example. (but also an exception, since it does > have a __len__ attribute. This is specifically part of range and not > generators in general, though.). > > However, range() is an example where the dunders could be valuable - > max(range(1e7)) already takes noticable time here, while it's rather > easy to figure it out from start stop and step, just like len now does > for it. > Have you ever written ``max(range(x))`` in production code? >
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