How to get part of string and pass it to other function in python?

Question

My task is to verify whether string is valid date and time or not.

\"2013-01-01W23:01:01\"

The date and the time are separated with

Answer 1

If all you need to do is to check whether the string in the format you specified is a valid datetime or not, no need to split it and pass values to some handmade functions, just use this:

from datetime import datetime

try:
    valid_datetime = datetime.strptime('2013-01-01W23:01:01', '%Y-%m-%dW%H:%M:%S')
    print 'this datetime is valid'
except ValueError:
    print 'this datetime is invalid'

Answer 2

You can try this ,

>>> a="2013-01-01W23:01:01"
>>> a.split('W')
['2013-01-01', '23:01:01']

And then send a.split('W')[0] and a.split('W')[1] to the validation functions.

Answer 3

Use str.partition() to get the first part, fast:

value.partition('W')[0]

You could use str.split() as well, for Python versions < 2.5. Limit the split to just the first W:

value.split('W', 1)[0]

Either technique will always yield a result, even if there is no 'W' character in value.

Demo:

>>> value = "2013-01-01W23:01:01"
>>> value.partition('W')[0]
'2013-01-01'
>>> value.split('W', 1)[0]
'2013-01-01'

Answer 4

If you are not sure whether it is a valid date or time, you should use regular expressions to validate the string, then you don't even need to call is_time and is_date.

import re
pattern = re.compile("^(\d{4}-\d{2}-\d{2})[W ](\d{2}:\d{2}:\d{2})$")
# ...
value = "2013-01-01W23:01:01"
match = pattern.findall(value)
if match:
  pass #is valid

This will test whether something looks like a date&time.

You can of course use more advanced regexes.

^(\d{4}-(11|12|0\d)-(3[10]|[12]\d))[W ]((2[0-3]|[01]\d):[0-5]\d:[0-5]\d)$

This one tests for valid date and time values (so it doesn't match 27:99:01 anymore), but still matches invalid dates, like 2014-02-31. If you want to exclude those cases, you can access the relevant parts of the match as items of the match variable and test for things like number of days of a month and leap years.