In [1]:

    

import re


    

In [2]:

    

pattern = re.compile(r'''
    ^
    (?P<year>\d{4})
    (?P<delimiter>[- /])
    (?P<month>\d{1,2})
    (?P=delimiter)  # must match earlier delimiter
    (?P<day>\d{1,2})
    $
''', re.VERBOSE)


    

In [3]:

    

foo = [
    '2016-7-6',
    '2016-07-06',
    '2016 07-06',
    '2016 07 06',
    '2016/07 06',
    '2016/07/06',
    '2016-07/06',
]


    

In [4]:

    

for s in foo:
    print('%r ' % s, end='')
    m = re.match(pattern, s)
    if not m:
        print('no match')
        continue
    print(
        'year=%s, month=%s, day=%s delimiter=%r' % (
        m.group('year'),
        m.group('month'),
        m.group('day'),
        m.group('delimiter'),
    ))


    

    




'2016-7-6' year=2016, month=7, day=6 delimiter='-'
'2016-07-06' year=2016, month=07, day=06 delimiter='-'
'2016 07-06' no match
'2016 07 06' year=2016, month=07, day=06 delimiter=' '
'2016/07 06' no match
'2016/07/06' year=2016, month=07, day=06 delimiter='/'
'2016-07/06' no match