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Date: Sun, 6 Apr 2014 07:31:05 -0500
From: Tim Chase <python.list@tim.thechases.com>
To: Ben Finney <ben+python@benfinney.id.au>
Subject: Re: How can I parse this correctly?
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On 2014-04-06 14:21, Ben Finney wrote:
> I assume you mean you will be creating =E2=80=98datetime.date=E2=80=99 ob=
jects. What
> will you set as the month and day?
>=20
> Alternatively, if you just want to do integer arithmetic on the
> year, you don't need the =E2=80=98datetime=E2=80=99 module at all.

Even if you do the arithmetic by hand, it's still nice to use the
datetime module to parse for sane dates:

  year =3D 2004
  month =3D 2
  day =3D 29

what should month & day be if you increment/decrement the year by
one?  The datetime module will throw a ValueError which is a nice
check for a valid date.  I've had to do things like this in a loop to
sanitize dates (depending on which field is being inc/dec'ed, by how
much, and which direction it's going) and it's nice to just have a

  y,m,d =3D initial =3D some_date.timetuple()[:3] #
  result =3D None
  while result is None:
    y,m,d =3D twiddle(y, m, d)
    try:
      result =3D datetime(y, m, d)
    except ValueError:
      result =3D None
  log.info("Shifted %r -> %r", initial, result)

where twiddle() is whatever business logic I need for this particular
case.  For me usually, it's adjusting by one month for billing
purposes.

-tkc