Python Error Handling concerning datetime and time

Question

I have this variable called pubdate which is derived from rss feeds. Most of the time it's a time tuple which is what I want it to be, so there are no errors.

Sometimes it's a unicode string, that's where it gets annoying.

So far, I have this following code concerning pubdate when it is a unicode string:

if isinstance(pubdate, unicode):
    try:
        pubdate = time.mktime(datetime.strptime(pubdate, '%d/%m/%Y %H:%M:%S').timetuple()) # turn the string into a unix timestamp
    except ValueError:
        pubdate = re.sub(r'\w+,\s*', '', pubdate) # removes day words from string, i.e 'Mon', 'Tue', etc.
        pubdate = time.mktime(datetime.strptime(pubdate, '%d %b %Y %H:%M:%S').timetuple()) # turn the string into a unix timestamp

But my problem is if the unicode string pubdate is in a different format from the one in the except ValueError clause it will raise another ValueError, what's the pythonic way to deal with multiple ValueError cases?

The datetime module can parse Mon as well. Post sample input/output if possible. — luoluo
– luoluo, Commented Oct 14, 2015 at 6:13
It's just a personal preference that I remove the Mon, Tue, etc.. An example input that would raise another ValueError would be pubdate = 10/14/2015 11:11 because it doesn't have seconds. That's something that I can't control because it's derived from an rss feed. I'm just having trouble handling multiple ValueError exceptions that will occur due to how pubdate is formatted. — hooliooo
– hooliooo, Commented Oct 14, 2015 at 6:21

luoluo · Accepted Answer · 2015-10-14 06:47:50Z

As you are parsing date string from a Rss. Maybe you need some guess when parsing the date string. I recommend you to use dateutil instead of the datetime module.

dateutil.parser offers a generic date/time string parser which is able to parse most known formats to represent a date and/or time.

The prototype of this function is: parse(timestr)(you don't have to specify the format yourself).

DEMO

>>> parse("2003-09-25T10:49:41")
datetime.datetime(2003, 9, 25, 10, 49, 41)

>>> parse("2003-09-25T10:49")
datetime.datetime(2003, 9, 25, 10, 49)

>>> parse("2003-09-25T10")
datetime.datetime(2003, 9, 25, 10, 0)

>>> parse("2003-09-25")
datetime.datetime(2003, 9, 25, 0, 0)

>>> parse("Sep 03", default=DEFAULT)
datetime.datetime(2003, 9, 3, 0, 0)

Fuzzy parsing:

>>> s = "Today is 25 of September of 2003, exactly " \
...     "at 10:49:41 with timezone -03:00."
>>> parse(s, fuzzy=True)
datetime.datetime(2003, 9, 25, 10, 49, 41,
              tzinfo=tzoffset(None, -10800))

This pretty much eliminated my need of multiple try and except methods for unicode date strings. Thank you

Martin Evans · Accepted Answer · 2023-07-12 08:17:33Z

You could take the following approach:

from datetime import datetime
import time

pub_dates = ['2/5/2013 12:23:34', 'Monday 2 Jan 2013 12:23:34', 'mon 2 Jan 2013 12:23:34', '10/14/2015 11:11', '10 2015']

for pub_date in pub_dates:
    pubdate = 0     # value if all conversion attempts fail
    
    for date_format in ['%d/%m/%Y %H:%M:%S', '%d %b %Y %H:%M:%S', '%a %d %b %Y %H:%M:%S', '%A %d %b %Y %H:%M:%S', '%m/%d/%Y %H:%M']:
        try:
            pubdate = time.mktime(datetime.strptime(pub_date, date_format).timetuple()) # turn the string into a unix timestamp
            break
        except ValueError as e:
            pass
    
    print(f'{pubdate:<12}  {pub_date}')

Giving output as:

1367493814.0  2/5/2013 12:23:34
1357129414.0  Monday 2 Jan 2013 12:23:34
1357129414.0  mon 2 Jan 2013 12:23:34
1444817460.0  10/14/2015 11:11
0             10 2015

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