Detect whether sequence is a multiple of a subsequence in Python

Question

I have a tuple of zeros and ones, for instance:

(1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1)

It turns out:

(1, 0, 1, 1, 1, 0, 1, 1, 1,          


        

Answer 1

Here's another solution (competing with my earlier iterators-based solution), leveraging numpy.

It does make a (single) copy of your data, but taking advantage of the fact your values are 0s and 1s, it is super-fast, thanks to numpy's magics.

import numpy as np

def is_reps(arr, slice_size):
    if len(arr) % slice_size != 0:
        return False
    arr = arr.reshape((-1, slice_size))
    return (arr.all(axis=0) | (~arr).all(axis=0)).all()

s = (1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1) * 1000
a = np.array(s, dtype=bool)
for i in range(1,len(s)):
    if is_reps(a, i):
        print i, s[:i]
        break