[Python-Dev] dateutil

[Greg Ewing]

> In dateutil, I think it's d + relativedelta(months=+1, day=1, days=-1).
> Arguably, this is fairly trivial (highly non-obvious, but trivial...)

Another thing that occurs to me. Presumably

  d + relativedelta(months=+1) + relativedelta(days=-1)

is not necessarily the same as

  d + relativedelta(days=-1) + relativedelta(months=+1)

so when you add two relativedeltas together, do you get
a relativedelta that does things in the right order?
In other words, can you do

  rd = relativedelta(days=-1) + relativedelta(months=+1)
  d += rd

and get the same result as

  d += relativedelta(days=-1)
  d += relativedelta(months=+1)

Also, there is presumably some order of precedence defined
when you specify multiple adjustments in one constructor.
>From your examples I'm guessing

  relativedelta(months=+1, days=-1) == \
    relativedelta(months=+1) + relativedelta(days=-1)

There could be a trap lurking here for the unwary, since
obviously then

  relativedelta(days=-1, months=+1) != \
    relativedelta(days=-1), relativedelta(months=+1)

Greg Ewing, Computer Science Dept, +--------------------------------------+
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