import re


def max_repetitions(s, threshold=8):
  """Find the largest contiguous repeating substring in s, repeating itself at
     least `threshold` times. Example:
     >>> max_repetitions("blablasbla")  # returns ['bla', 2]."""
  repetitions_re = re.compile(r'(.+?)\1{%d,}' % threshold)
  max_repeated = None
  for match in repetitions_re.finditer(s):
    new_repeated = [match.group(1), len(match.group(0))/len(match.group(1))]
    # pylint: disable=unsubscriptable-object
    if max_repeated is None or max_repeated[1] < new_repeated[1]:
      max_repeated = new_repeated
  return max_repeated