Parsing a date that can be in several formats in python
I would like to parse a date that can come in several formats, that I know beforehand. If I could not parse, I return nil. In ruby, I do like this:
DATE_FORMATS = ['%m/%d/%Y %I:%M:%S %p', '%Y/%m/%d %H:%M:%S', '%d/%m/%Y %H:%M', '%m/%d/%Y', '%Y/%m/%d']
def parse_or_nil(date_str)
parsed_date = nil
DATE_FORMATS.each do |f|
parsed_date ||= DateTime.strptime(date_str, f) rescue nil
end
parsed_date
end
This is concise and works. How can I do the same thing in Python?
I would just try dateutil. It can recognize most of the formats:
from dateutil import parser
parser.parse(string)
if you end up using datetime.strptime as suggested @RocketDonkey:
from datetime import datetime
def func(s,flist):
for f in flist:
try:
return datetime.strptime(s,f)
except ValueError:
pass
You can use try/except
to catch the ValueError
that would occur when trying to use a non-matching format. As @Bakuriu mentions, you can stop the iteration when you find a match to avoid the unnecessary parsing, and then define your behavior when my_date
doesn't get defined because not matching formats are found:
You can use try/except
to catch the ValueError
that would occur when trying to use a non-matching format:
from datetime import datetime
DATE_FORMATS = ['%m/%d/%Y %I:%M:%S %p', '%Y/%m/%d %H:%M:%S', '%d/%m/%Y %H:%M', '%m/%d/%Y', '%Y/%m/%d']
test_date = '2012/1/1 12:32:11'
for date_format in DATE_FORMATS:
try:
my_date = datetime.strptime(test_date, date_format)
except ValueError:
pass
else:
break
else:
my_date = None
print my_date # 2012-01-01 12:32:11
print type(my_date) # <type 'datetime.datetime'>
After your tip, RocketDonkey, and the one from Bakuriu, I could write a shorter version. Any problem with it?
def parse_or_none(date):
for date_format in DATE_FORMATS:
try:
return datetime.strptime(date, date_format)
except ValueError:
pass
return None
Modifying root's answer to handle m/d/y:
from dateutil import parser
parser.parse(string, dayfirst=False)
There's also a yearfirst option, to prefer y/m/d.