[Python-Dev] dateutil (original) (raw)

Greg Ewing greg at cosc.canterbury.ac.nz
Sun Mar 14 22:17:50 EST 2004

Some thoughts about this relativedelta stuff:

Isn't the name "relativedelta" somewhat superfluouslyredundant? The word "delta" already implies something relative. (It's also ratherhardtoread.)

>>> d datetime.datetime(2004, 4, 4, 0, 0) >>> d+relativedelta(month=1) datetime.datetime(2004, 1, 4, 0, 0)

So a relativedelta can affect things in a way that's not relative at all? That sounds very confusing.

Wouldn't it be better if relativedelta confined itself to relative things only, and provide some other way of absolutely setting fields of a date?

MO(0) shouldn't be used as it makes no sense, but is the same as MO(+1) which is the same as MO(1).

So there is a hole at 0. Something about that smells wrong.

The expected type [of leapdays] is an integer. This is mainly used to implement nlyearday.

Would a value other than 0 or 1 ever make sense for this? I'm having a hard time imagining how it could -- but maybe my imagination isn't twisted enough...

> Is it true that adding relativedelta(months=+1) 12 times isn't necessarily > the same as adding relativedelta(years=+1) once?

They land on the same date. While the documentation looks somewhat confusing, the implementation is not. For example: >>> date(2000,2,29)+relativedelta(months=+12) datetime.date(2001, 2, 28)

I think the OP's question was what happens if you do

for i in range(12): d += relativedelta(months=+1)

Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | A citizen of NewZealandCorp, a | Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. | greg at cosc.canterbury.ac.nz +--------------------------------------+

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