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

data = np.random.randn(7, 3)

Number of positive values:

(data > 0).sum()

12

Number of negative values:

(data < 0).sum()

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 = np.random.randn(7, 3)

bools = data > data2

bools

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

bools.any()

True

bools.all()

False