Python finding repeating sequence in list of integers?

Question

I have a list of lists and each list has a repeating sequence. I'm trying to count the length of repeated sequence of integers in the list:

list_a = [111,0,3,1,111,0,3,1,111,0,3,1] 

list_b = [67,4,67,4,67,4,67,4,2,9,0]

list_c = [1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,23,18,10]

Which would return:

list_a count = 4 (for [111,0,3,1])

list_b count = 2 (for [67,4])

list_c count = 10 (for [1,2,3,4,5,6,7,8,9,0])

Any advice or tips would be welcome. I'm trying to work it out with re.compile right now but, its not quite right.

Solution

Guess the sequence length by iterating through guesses between 2 and half the sequence length. If no pattern is discovered, return 1 by default.

def guess_seq_len(seq):
    guess = 1
    max_len = len(seq) / 2
    for x in range(2, max_len):
        if seq[0:x] == seq[x:2*x] :
            return x

    return guess

list_a = [111,0,3,1,111,0,3,1,111,0,3,1] 
list_b = [67,4,67,4,67,4,67,4,2,9,0]
list_c = [1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,23,18,10]

print guess_seq_len(list_a)
print guess_seq_len(list_b)
print guess_seq_len(list_c)
print guess_seq_len(range(500))   # test of no repetition

This gives (as expected):

4
2
10
1

As requested, this alternative gives longest repeated sequence. Hence it will return 4 for list_b. The only change is guess = x instead of return x

def guess_seq_len(seq):
    guess = 1
    max_len = len(seq) / 2
    for x in range(2, max_len):
        if seq[0:x] == seq[x:2*x] :
            guess = x

    return guess