Methods for Boolean arrays

Boolean values have been converted to 1 (True) and 0 (False) in the previous methods. Therefore, sum is often used to count the True values in a Boolean array:

import numpy as np

rng = np.random.default_rng()
data = rng.normal(size=(7, 3))

Number of positive values:

(data >= 0).sum()

np.int64(12)

Number of negative values:

(data < 0).sum()

np.int64(9)

There are two additional methods, any and all, which are particularly useful for Boolean arrays:

• any checks whether one or more values in an array are true

• all checks whether each value is true

data2 = rng.normal(size=(7, 3))
bools = data > data2

bools

array([[False, False, False],
       [False,  True,  True],
       [False, False, False],
       [False,  True, False],
       [False,  True, False],
       [ True,  True,  True],
       [ True,  True,  True]])

bools.any()

np.True_

bools.all()

np.False_