stripping time from a string in python

Question

I am trying to strip off the time stamp from a string for e.g. '9/10/20151:03 PM' Note that there is intentionally no space between the date and time.
Here's the code:

datetime.strptime(date, "%m/%d/%Y%I:%M %p")

However, I might get bad strings like '9/10/2015 1:03 PM' ( with a space between date and time). I am contemplating to grep the incoming string for a pattern and decide which pattern to use in my strptime method.

My question is that is there a better way to do this? I looked at documentation of strptime method and it doesn't support multiple patterns. The only other way I can think of is following ( but it doesn't support more than two patterns )

try:
    time = datetime.strptime(date, "%m/%d/%Y%I:%M %p")
except Exception as e:
    time = datetime.strptime(date, "%m/%d/%Y %I:%M %p")

CONSTRAINTS: 1. Cannot depend on a library except datetime since I am going to push it to production as a bug fix.

Joran Beasley · Accepted Answer · 2015-09-11 00:21:04Z

1

$ pip install python-dateutil


...
>>> from dateutil.parser import parse
>>> print parse(my_date_string)

the dateutil library does a great job of converting any string to a date and its almost always right ...

without using it you could certainly do something like

date = date_string[:10] # mm/dd/YYYY
rest = strip(date_string[10:]
timestamp = date+" "+rest

edited Sep 11, 2015 at 0:21

answered Sep 11, 2015 at 0:15

Joran Beasley

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3 Comments

nick01 Over a year ago

Thanks Joran. I am going to be pushing the code to production hence not looking for dependency on a library. I will mention that in the question.

Joran Beasley Over a year ago

in that case you know the date is always the first 10 characters

nick01 Over a year ago

nah that won't work. '9/10/20151:03 PM' results into '9/10/20151 :03 PM' [ wrong] '12/10/20151:03 PM' results into '12/10/2015 1:03 PM'[correct]

bgporter · Accepted Answer · 2015-09-11 00:49:52Z

Something like:

from datetime import datetime

# more patterns as you need.
PATTERNS = ["%m/%d/%Y%I:%M %p", "%m/%d/%Y %I:%M %p"]

def GetDate(dateStr):
   '''
      Attempt to parse a string and create a datetime.datetime object
      using a list of potential date format patterns. Returns None if 
      it's unable to make sense of the string as a date. 

      >>> GetDate("3/1/20154:15 PM")
      datetime.datetime(2015, 3, 1, 16, 15)
      >>> GetDate("3/1/2015 4:15 PM")
      datetime.datetime(2015, 3, 1, 16, 15)
      >>> GetDate("not a date")
      >>>

   '''
   for pattern in PATTERNS:
      try:
         return datetime.strptime(dateStr, pattern)
      except ValueError:
         # loop to the next pattern
         continue
   return None


if __name__ == "__main__":
   import doctest
   doctest.testmod()

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