thebjorn wrote:
> John Machin wrote:
> > thebjorn wrote:
> [...]
> > >
> > > def age(born):
> > > now = date.today()
> > > birthday = date(now.year, born.month, born.day)
> >
> > Bad luck if the punter was born on 29 Feb and the current year is not a
> > leap year.
>
> Good catch! Thanks!
Easy catch -- happens at least one per inning[s] :-)
>
> [..]
> > Holy code bloat, Batman! Try this:
> >
> > return now.year - born.year - (birthday > now)
>
> yuck :-)
But this:
return now.year - born.year - (birthday > now and 1 or 0)
is not yuck???
>
> [...]
> > It's the irregular-size months that cause the problems. If you can work
> > out the months difference, then just floor_div by 12 to get the years
> > difference.
>
> I don't agree that the irregular sized months cause a problem in this
> case. They do cause a problem if you're asking "when is today + one
> month?", i.e. there isn't an unambiguous answer to that question in
> general (e.g. if today was January 31). We're asking a different kind
> of question though: "has it been at least one month since January 31?",
> the answer would be no on Feb 29 and yes on Mar 1.
If a bank were paying you interest on a monthly basis, and you
deposited money on Jan 31 and pulled it out on the last day of
February, that would count as one month. This is what I call the "today
- yesterday == 1" rule. For computing things like duration of employee
service, you need the "today - yesterday == 2" rule -- on the
assumption that service counts from start of business yesterday to
close of business today. So hire date of 1 Feb to fire date of (last
day of Feb) would count as one month.
>
> > Below is some code from the ancient times when everybody and his dog
> > each had their own date class :-)
> [...]
>
> Wow. I'm speechless. (any reason you didn't want to use the calendar
> module?)
Sorry, I don't understand. Why are you speechless? What would I want to
use the calendar module for? Apart from the leap() function and the
table of days in a month, the calendar module doesn't have any of the
functionality that one would expect in a general-purpose date class.
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