Yeah, sadly the point where we *should* have made this clean break was in 3.0. That's where e.g. inequalities between a string and a number, or between either type and None, were changed from returning something "arbitrary but stable" into raising TypeError. It's much harder to break it now, even with endless deprecation warnings. We might want to try again in 4.0. :-)
On Tue, Sep 22, 2015 at 1:25 PM, Tim Peters <tim.pet...@gmail.com> wrote: > [Guido] > >> it is broken, due to the confusion about classic vs. timeline arithmetic > >> -- these have different needs but there's only one > operator. > > [Alex] > > I feel silly trying to defend a design against its author. :-) > > "Design" may be an overstatement in this specific case ;-) > > I remember implementing this stuff, getting to the comparison > operators, and noting that the spec was silent about what to do in > case the tzinfos differed. I looked at Guido and explained that, and > asked "so whaddya wanna do?". > > One of us (I don't recall which) said "well, we could convert to UTC > first - that would make sense". "Ya, sure," said the other. And I > said "and then, of course, interzone subtraction should do the same." > "Of course," said Guido, now annoyed that I was bothering him with the > obvious ;-) > > Note that, near that time, Python blithely compared _any_ two objects, > even if of wildly different types. Compared to that, doing _anything_ > arguably sane with datetime objects seemed wildly desirable. > Ironically, the datetime implementation was Python's first library > type to _refuse_ to compare its objects to others of wildly different > types. > > So, in all, I'd say well under a minute's thought - between us - went > into this decision. And we've been living in Paradise ever since :-) > > > > Yes, a language with more than one > symbol would not have some > > of these problems. Similarly a language with a special symbol for > > string catenation would not have a non-commutative + and non- > > distributive *. All I am saying is that I can live with the choices made > > in datetime. > > Given that the alternative is suicide, I approve of that life decision. > -- --Guido van Rossum (python.org/~guido)
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