[Python-Dev] proposal: add basic time type to the standard library (original) (raw)

Jim Fulton jim@zope.com
Tue, 26 Feb 2002 16:23:42 -0500

Guido van Rossum wrote:

> > The timetuple() method provides access to all of these > > simultaneously. Isn't that enough? > > From a minimalist point of view, yet, but from a usability point > of view, no. > > > t.year() could be spelled as > > t.timetuple()[0]. > > Yes, but t.year() is a lot more readable. When do you ever use this in isolation? I'd expect in 99% of the cases you hand it off to a formatting routine, and guess what -- strftime() takes a time tuple. I worry about the time wasted by calling all of t.year(), t.month(), t.day() (etc.) -- given that they do so little, the call overhead is probably near 100%. I wonder how often this is needed. The only occurrences of year() in the entire Zope source that I found are in various test routines.

These methods and others are used a lot in presentation code, which tends to be expressed in DTML or ZPT.

It's not uncommon to select/catagorize things by year or month.

I think most people would find individual date-part methods a lot more natural than tuples.

> > I expect that usually you'd request several of > > these together anyway, in order to do some fancy formatting, so the > > timetuple() approach makes sense. > > I find the time tuples to be really inconvenient. I always > have to slice off the parts I don't want, which I find annoying.

Serious question: what do you tend to do with time values?

I format them in various ways and I sort them.

I imagine that once we change strftime() to accept an abstract time object, you'll never need to call either timetuple() or year() -- strftime() will do it for you.

Maybe, if I use strftime, but I don't use strftime all that much. I can certainly think of even formatting cases (e.g. internationalized dates) where it's not adequate.

> Hm, now that I mention the extra parts, it seems kind of silly > to make implementors of the type come up with weekday, julian day, and > a daylight-savings flag. This time format is really biased by > the C time library, which is fine for a module that wraps the C library > but seems a bit silly for a standard date-time interface.

That's why /F's pre-PEP allows the implementation to leaves these three set to -1.

I missed these. Still, providing -1s seems, uh, vestigial.

> > > with date parts > > > being one based and time parts being zero based. > > > > I'm not sure what you mean here. > > Years, months, and days should start from 1. > Hours, minutes and seconds should start from 0. > > One confusion I often have with time tuples is that I know > too much about C's time struct, which numbers months from 0 > and which has years since 1900.

I guess that confusion is yours alone. In Python, of course month and day start from 1. Whether years start from 1 is a theological question. :-)

I doubt the confusion is mine alone, but I'll take your word for it.

Jim

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