常量

numpy.nan

• 表示空值。

  nan = NaN = NAN

【例】两个numpy.nan是不相等的。

import numpy as np
print(np.nan == np.nan)  # False
print(np.nan != np.nan)  # True

• numpy.isnan(x, *args, **kwargs) Test element-wise for NaN and return result as a boolean array.

【例】

import numpy as np
x = np.array([1, 1, 8, np.nan, 10])
print(x)
# [ 1.  1.  8. nan 10.]
y = np.isnan(x)
print(y)
# [False False False  True False]
z = np.count_nonzero(y)
print(z)  # 1

numpy.inf

• 表示正无穷大。

  Inf = inf = infty = Infinity = PINF

  numpy.pi

• 表示圆周率

  pi = 3.1415926535897932384626433...

  numpy.e

• 表示自然常数

  e = 2.71828182845904523536028747135266249775724709369995...