Parsing a date in python without using a default

Question

I\'m using python\'s dateutil.parser tool to parse some dates I\'m getting from a third party feed. It allows specifying a default date, which itself defaults

Answer 1

Depending on your domain following solution might work:

DEFAULT_DATE = datetime.datetime(datetime.MINYEAR, 1, 1)

def parse_no_default(dt_str):    
    dt = parser.parse(dt_str, default=DEFAULT_DATE).date()
    if dt != DEFAULT_DATE:
       return dt
    else:
       return None

Another approach would be to monkey patch parser class (this is very hackiesh, so I wouldn't recommend it if you have other options):

import dateutil.parser as parser
def parse(self, timestr, default=None,
          ignoretz=False, tzinfos=None,
          **kwargs):
    return self._parse(timestr, **kwargs)
parser.parser.parse = parse

You can use it as follows:

>>> ffffd = parser.parser().parse('2011-01-02', None)
>>> ffffd
_result(year=2011, month=01, day=02)
>>> ffffd = parser.parser().parse('2011', None)
>>> ffffd
_result(year=2011)

By checking which members available in result (ffffd) you could determine when return None. When all fields available you can convert ffffd into datetime object:

# ffffd might have following fields:
# "year", "month", "day", "weekday",
# "hour", "minute", "second", "microsecond",
# "tzname", "tzoffset"
datetime.datetime(ffffd.year, ffffd.month, ffffd.day)