Using strings

Another seemingly clever solution is to convert the lists to strings and then use the in operator to check for sub-sequences. Note that this approach, even if it worked, is not as performant as the previous one.

SUBLIST = 1
SUPERLIST = 2
EQUAL = 3
UNEQUAL = 4

def sublist(list_one, list_two):
    list_one_check = str(list_one).strip("[]")
    list_two_check = str(list_two).strip("[]")

    if list_one_check == list_two_check:
        return EQUAL
    elif list_one_check in list_two_check:
        return SUBLIST
    elif list_two_check in list_one_check:
        return SUPERLIST
    return UNEQUAL

Let's parse the code to see what it does. In this approach, we convert the lists to strings, so [1, 2, 3] becomes "[1, 2, 3]", remove the brackets "1, 2, 3", and add a comma "1, 2, 3,". We check equality and then use the in operator to check for SUBLIST or SUPERLIST, and finally return UNEQUAL.

We add a comma because, say, we call sublist with [1, 2] and [1, 22]. "1, 2" in "1, 22" evaluates to True, so the function would wrongly mark it as SUBLIST.

This test can be overridden by changing the code like this:

list_one_check = str(list_one).strip("[]") + ','
list_two_check = str(list_two).strip("[]") + ','

Yet, the test case (which doesn't exist in the Exercism test suite) ["1", "2"] and ["5", "'1', '2',", "7"] would fail.

Students can add any arbitrary string into the representation to try to "defeat" this test - list_one_check = str (list_one) + TOKEN. The test suite currently test TOKEN = '', but not others.