def count_length_two_runs_in_sequence(sequence):
"""Count length-``2`` runs in `sequence`:
::
>>> sequencetools.count_length_two_runs_in_sequence([0, 0, 1, 1, 1, 2, 3, 4, 5])
3
Returns nonnegative integer.
"""
total_repetitions = 0
for left, right in iterate_sequence_pairwise_strict(sequence):
if left == right:
total_repetitions += 1
return total_repetitions
def is_repetition_free_sequence(expr):
'''True when `expr` is a sequence and `expr` is repetition free:
::
>>> sequencetools.is_repetition_free_sequence([0, 1, 2, 6, 7, 8])
True
False when `expr` is a sequence and `expr` is not repetition free:
::
>>> sequencetools.is_repetition_free_sequence([0, 1, 2, 2, 7, 8])
False
True when `expr` is an empty sequence:
::
>>> sequencetools.is_repetition_free_sequence([])
True
False `expr` is not a sequence:
::
>>> sequencetools.is_repetition_free_sequence(17)
False
Returns boolean.
'''
try:
for left, right in iterate_sequence_pairwise_strict(expr):
if left == right:
return False
return True
except TypeError:
return False
