Convert a date string into YYYYMMDD

You can almost do this with a combination of strptime and strptime from the datetime module.

The problem we have is that the built-in formats support dates like 30 November 2010 but not 30th November 2010. So in the example below I've used a regular expression substitution to strip out the problem characters. (The regular expression uses a look-behind to see if "st", "nd", "rd" or "th" is preceeded by a digit, and if so replaces it with the empty string, thus removing it from the string.)

>>> import re
>>> from datetime import datetime
>>> mydate = "30th November 2009"
>>> mydate = re.sub("(?<=\d)(st|nd|rd|th)","",mydate)
>>> mydate
'30 November 2009'
>>> mydatetime = datetime.strptime(mydate,"%d %B %Y")
>>> mydatetime
datetime.datetime(2009, 11, 30, 0, 0)
>>> mydatetime.strftime("%Y%M%d")
'20090030'

Try dateutil:

from dateutil import parser

dates = ['30th November 2009', '31st March 2010', '30th September 2010']

for date in dates:
    print parser.parse(date).strftime('%Y%m%d')

output:

20091130
20100331
20100930

or if you want to do it using standard datetime module:

from datetime import datetime

dates = ['30th November 2009', '31st March 2010', '30th September 2010']

for date in dates:
    part = date.split()
    print datetime.strptime('%s %s %s' % (part[0][:-2]), part[1], part[2]), '%d %B %Y').strftime('%Y%m%d')