Is it reliable to compare two isoformat datetime strings?

Question

I need to find out which of two isoformatted datetime strings is the latest.

By now, I convert them using datetime.strptime method. Then I compare two datetime objects. Then I call isoformat of the greatest datetime object in order to pass it as a get parameter.

So I'm wondering if it is reliable to find out the greatest isoformatted string without doing converstion from str to datetime.

It seems to work:

>>> from datetime import datetime as dt
>>> s1 = '2013-12-25T19:20:41.391393'
>>> s2 = '2013-12-25T19:20:41.391394'
>>> s1 > s2
False
>>> pattern = '%Y-%m-%dT%H:%M:%S.%f'
>>> dt.strptime(s1, pattern) > dt.strptime(s2, pattern)
False

Answer 1

ISO 8601 date strings (without timezone offset), which is the type of string returned by isoformat, can be compared as strings.

As Assem-Hafez points out, if the strings include timezone offsets, then string comparison may not produce the same result as timezone-aware datetime comparison:

In [31]: import dateutil.parser as DP

In [32]: s = ["2019-08-29T10:50:35+00:00", "2019-08-29T10:50:35+02:00"]

In [33]: t = [DP.parse(si) for si in s]; t
Out[33]: 
[datetime.datetime(2019, 8, 29, 10, 50, 35, tzinfo=tzutc()),
 datetime.datetime(2019, 8, 29, 10, 50, 35, tzinfo=tzoffset(None, 7200))]

In [34]: s[0] < s[1]
Out[34]: True

In [35]: t[0] < t[1]
Out[35]: False