robust method to parse time string to datetime using dateutil parser

Convert time strings into datetime format coudd be very tedious, because we need to make sure the every new data
follow the exact format required by the conversion functions, otherwise it will raise error.

One good way is to user the dateutil.parser package, which is much more flexiable. It can also support some fuzziness.
With this package, even some data has slightly different formats than we expect, it will not cause error.

The traditional way to convert time string to datatime format

import datetime

# without milliseconds format
item = '2022/01/01 10:49:12'
result = datetime.datetime.strptime(item, "%Y/%m/%d %H:%M:%S")

print(result.year)

# with milliseconds format
item = '2022/01/01 10:49:12.213'
result = datetime.datetime.strptime(item, "%Y/%m/%d %H:%M:%S.%f")

print(result.year)

# in the above example if there is a new item that doesn't follow the milliseconds format, it will raise error
item = '2022/01/01 10:49:12'
result = datetime.datetime.strptime(item, "%Y/%m/%d %H:%M:%S.%f")

print(result.year)

2022
2022



---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)

<ipython-input-20-a29c39b3ca30> in <module>
     15 # in the above example if there is a new item that doesn't follow the milliseconds format, it will raise error
     16 item = '2022/01/01 10:49:12'
---> 17 result = datetime.datetime.strptime(item, "%Y/%m/%d %H:%M:%S.%f")
     18 
     19 print(result.year)


D:\Anaconda3\lib\_strptime.py in _strptime_datetime(cls, data_string, format)
    575     """Return a class cls instance based on the input string and the
    576     format string."""
--> 577     tt, fraction, gmtoff_fraction = _strptime(data_string, format)
    578     tzname, gmtoff = tt[-2:]
    579     args = tt[:6] + (fraction,)


D:\Anaconda3\lib\_strptime.py in _strptime(data_string, format)
    357     if not found:
    358         raise ValueError("time data %r does not match format %r" %
--> 359                          (data_string, format))
    360     if len(data_string) != found.end():
    361         raise ValueError("unconverted data remains: %s" %


ValueError: time data '2022/01/01 10:49:12' does not match format '%Y/%m/%d %H:%M:%S.%f'

use parser in dateutil package, a more stable way

from dateutil.parser import *

# for the same example above, it will not raiser error

item = '2022/01/01 10:49:12'
result = parse(item)
print(result.year)


item = '2022/01/01 10:49:12.213'
result = parse(item)
print(result.year)

2022
2022