>>> import numpy as np
>>> from scipy.spatial.distance import hamming
>>> a = np.array([0, 1, 1, 0], dtype=bool)
>>> b = np.array([0, 1, 1], dtype=bool)
>>> hamming(a, b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  [...] spatial/distance.py", line 369, in hamming
    return np.not_equal(u, v).mean()
ValueError: operands could not be broadcast together with shapes (4,) (3,) 
>>> hamming(b, b)
0.0
>>> hamming(b, np.logical_not(b))
1.0