[Baypiggies] custom date parser
Aaron Maxwell
amax at redsymbol.net
Wed Sep 3 21:53:18 CEST 2008
On Wednesday 03 September 2008 11:22:15 am you wrote:
> Assuming you want exactly the functionality you've coded
That is correct.
> (as opposed
> to a more general fuzzy parse as Anna suggests), the key to making it
> more compact is seeing that what you're doing in your code is an
> unrolled loop -- and rolling it up again. E.g., after the initial
> assignment to parts, the rest of the code could be:
>
> for i in range(1, 4):
> try: return datetime.datetime(*parts)
> except ValueError: parts[-i] = 1
> return None
That is the insight I was looking for. Thanks Alex.
Anna, thanks for suggesting dateutils - not what's needed for this particular
problem, but I was not familiar with it.
Aaron
>
> On Wed, Sep 3, 2008 at 10:12 AM, Aaron Maxwell <amax at redsymbol.net> wrote:
> > Hi all,
> >
> > Below is a function that parses a date string in the form "YYYY-MM-DD"
> > and returns a datetime.date object, or None if it's bad input and
> > cannot be converted. However, it does a couple of special tricks.
> > The data in certain cases is known to have a value for the day or
> > month that is not in the valid range; e.g., it may be 2007-11-31
> > (November traditionally only has 30 days), or 2002-14-23. In this
> > situation, I want to keep the most signficant good field(s) and set
> > the lessors to 1, then return the date object from that - so the
> > results of the above would be date(2007, 11, 1) or date(2002, 1, 1)
> > respectively.
> >
> > The function below does this. It uses a triply-nested try/except
> > block, and I can't shake the feeling that there is a shorter and
> > clearer implementation. Any thoughts?
> >
> > Of course, one approach would be to manually check that the month and
> > day field before passing them to datetime.date. I would rather reuse
> > the validation code in the date class, though, for obvious reasons.
> >
> > Thanks in advance,
> > Aaron
> >
> > {{{
> > import datetime
> > def parse_datefield(raw_pubdate):
> > '''
> > Parse a datefield
> > Takes in a date string in the format YYYY-MM-DD.
> > Returns a datetime.date object.
> > '''
> > # ... imagine validation/error checking code here ...
> > parts = map(int, raw_pubdate.split('-'))
> > try:
> > d = datetime.date(*parts)
> > except ValueError:
> > # day out of range?
> > parts[-1] = 1
> > try:
> > d = datetime.date(*parts)
> > except ValueError:
> > # month out of range?
> > parts[-2] = 1
> > try:
> > d = datetime.date(*parts)
> > except ValueError:
> > # give up
> > d = None
> > return d
> > }}}
> >
> > --
> > Aaron Maxwell
> > http://redsymbol.net
> > _______________________________________________
> > Baypiggies mailing list
> > Baypiggies at python.org
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> > http://mail.python.org/mailman/listinfo/baypiggies
--
Aaron Maxwell
http://redsymbol.net
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