Python Date format validator

12 Nov 2013

Post first published in nixtip

Simplicity is always best and Python makes this task insanely easy.

We just only need to take advantage of the strptime function of the time module.

As usually in Python, the code is pretty self-explanatory:

#!/usr/bin/python
"""date_validator.py"""
import time

def check_format(datec):
    # checks YYYYMMDD / YYYY-MM-DD / DDMMYYYY and MMDDYYYY formats

    format_ok = False
    for mask in ['%Y%m%d','%Y-%m-%d','%d%m%Y','%m%d%Y']:
    try:
        time.strptime(datec, mask)
        format_ok = True
        break
    except ValueError:
        pass

    if format_ok:
        print "Correct date !:%12s mask:%s" % (datec,mask)
    else:
        print "KO: %s" % datec
    return None

def main():
    check_format('11082011')
    check_format('12312010')
    check_format('13312010')
    check_format('20110811')
    check_format('40118841')
    check_format('2012-02-29')
    check_format('20110229')

if __name__=="__main__":
    main()

./date_validator.py
Correct date !:    11082011 mask:%d%m%Y
Correct date !:    12312010 mask:%m%d%Y
KO: 13312010
Correct date !:    20110811 mask:%Y%m%d
KO: 40118841
Correct date !:  2012-02-29 mask:%Y-%m-%d
Correct date !:    20110229 mask:%d%m%Y

If we use the interpreter it couldn’t be more clear.

Choose a good pair of date + mask and the result will be fine:

>>> import time
>>> datec='20110811'
>>> time.strptime(datec,'%Y%m%d')
time.struct_time(tm_year=2011, tm_mon=8, tm_mday=11, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=223, tm_isdst=-1)

Otherwise:

>>> time.strptime(datec,'%m%d%Y')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib64/python2.6/_strptime.py", line 454, in _strptime_time
return _strptime(data_string, format)[0]
File "/usr/lib64/python2.6/_strptime.py", line 328, in _strptime
data_string[found.end():])
ValueError: unconverted data remains: 1

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Python Date format validator