numpy.isnan() in Python

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The numpy.isnan() function tests element-wise whether it is NaN or not and returns the result as a boolean array. Syntax :

numpy.isnan(array [, out])

Parameters :

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.

Return :

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.

Code 1 :

Python

Output :

Is NaN :  False 

Is NaN :  False 

Is NaN :  True 

Is NaN :  False 

Is NaN :  False 

Checking for NaN :  [0 0 0]

Code 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))

Output :

 [[ 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]]

References : https://docs.scipy.org/doc/numpy-dev/reference/generated/numpy.isnan.html

Note : These codes won’t run on online IDE’s. So please, run them on your systems to explore the working.

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Last Updated : 28 Mar, 2022