python to diff two lists of datetime strings, each with their own format

differ.py

from datetime import datetime


def diff_datewise(left, right, left_format=None, right_format=None):
    """
    Parameters
        left            : a list of datetime strings or objects
        right           : a list of datetime strings or objects
        left_format     : None if left contains datetimes, or strptime format
        right_format    : None if right contains datetimes, or strptime format

    Returns
        A tuple of two sets:
        [0] : the datetime objects in left but not right
        [1] : the datetime objects in right but not left
    """
    
    if left_format:
        left_set = set([datetime.strptime(l, left_format) for l in left])
    else:
        left_set = set(left)
    
    if right_format:
        right_set = set([datetime.strptime(r, right_format) for r in right])
    else:
        right_set = set(right)
    
    return (left_set - right_set, right_set - left_set)


# test
print('')
print('*********** TEST SETUP **********')
from time import time

l = []
l_just_dates = []
r = []
lf = 'blah%Y...%m...%d...%Hblahblah'
rf = 'neenee%Y%m%d%Hneenee'

expect_0 = set([datetime(2002, 6, 14, 13), datetime(2010, 11, 9, 3)])
expect_1 = set([datetime(2012, 6, 14, 13), datetime(2001, 11, 10, 22)])

for y in range(2001,2014):
    for m in range(1,13):
        # we're just diffing so we don't care about getting all days
        for d in range(1,28):
            for h in range(0,24):
                x = datetime(y, m, d, h)
                if not x in expect_1:
                    l.append(datetime.strftime(x, lf))
                    l_just_dates.append(x)
                if not x in expect_0:
                    r.append(datetime.strftime(x, rf))

print('')
print('************ TEST 1 *************')
start = time()
result = diff_datewise(l, r, left_format=lf, right_format=rf)
end = time()
print(result)
print('left diff correct: {0}'.format(result[0] == expect_0))
print('right diff correct: {0}'.format(result[1] == expect_1))
print('time elapsed: {0}'.format(end-start))

print('')
print('************ TEST 2 *************')
start = time()
result = diff_datewise(l_just_dates, r, left_format=None, right_format=rf)
end = time()
print(result)
print('left diff correct: {0}'.format(result[0] == expect_0))
print('right diff correct: {0}'.format(result[1] == expect_1))
print('time elapsed: {0}'.format(end-start))

print('')
print('')