Python中的 numpy.isnan()

numpy.isnan()函数按元素测试它是否为 NaN，并将结果作为布尔数组返回。句法 ：

numpy.isnan(array [, out])

参数 ：

array : [array_like]Input array or object whose elements, we need to test for infinity
out   : [ndarray, optional]Output array placed with result.
      Its type is preserved and it must be of the right shape to hold the output.

返回 ：

boolean array containing the result. For scalar input, the result is a new boolean with value
True if the input is positive or negative infinity; otherwise the value is False.
For array input, the result is a boolean array with the same shape as the input and the values
are True where the corresponding element of the input is positive or negative infinity; 
elsewhere the values are False.

代码 1：

Python

# Python Program illustrating
# numpy.isnan() method
  
import numpy as geek
 
print("Is NaN : ", geek.isnan(1), "\n")
 
print("Is NaN : ", geek.isnan(0), "\n")
 
# not a number
print("Is NaN : ", geek.isnan(geek.nan), "\n")
 
#  infinity
print("Is NaN : ", geek.isnan(geek.inf), "\n")
 
print("Is NaN : ", geek.isnan(geek.NINF), "\n")
 
x = geek.array([-geek.inf, 0., geek.inf])
y = geek.array([2, 2, 2])
print("Checking for NaN : ", geek.isnan(x, y))

输出 ：

Is NaN :  False 

Is NaN :  False 

Is NaN :  True 

Is NaN :  False 

Is NaN :  False 

Checking for NaN :  [0 0 0]

代码 2：

Python

# Python Program illustrating
# numpy.isnan() method
   
import numpy as geek
  
# Returns True/False value for each element
b = geek.arange(20).reshape(5, 4)
                
print("\n",b)
print("\nIs NaN(Not a Number): \n", geek.isnan(b))
 
 
b = [[1j],
     [geek.nan]]
print("\nIs NaN(Not a Number) : \n", geek.isnan(b))

输出 ：

[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]
 [16 17 18 19]]

Is NaN(Not a Number): 
 [[False False False False]
 [False False False False]
 [False False False False]
 [False False False False]
 [False False False False]]

Is NaN(Not a Number) : 
 [[False]
 [ True]]

参考资料： https://docs.scipy.org/doc/numpy-dev/reference/generated/numpy.isnan.html

注意：这些代码不会在在线 IDE 上运行。因此，请在您的系统上运行它们以探索其工作原理。