numpy.isnan() in Python Last Updated : 08 Mar, 2024 Comments Improve Suggest changes Like Article Like Report 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 # 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)) 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]] Note : These codes won't run on online IDE's. So please, run them on your systems to explore the working. Comment More infoAdvertise with us Next Article numpy.isnan() in Python M Mohit Gupta_OMG Improve Article Tags : Python Python-numpy Python numpy-Logic Functions Practice Tags : python Similar Reads numpy.isinf() in Python The numpy.isinf() function tests element-wise whether it is +ve or -ve infinity or not return the result as a boolean array. Syntax: numpy.isinf(array [, out]) Parameters :  array : [array_like]Input array or object whose elements, we need to test for infinity out : [ndarray, optional]Output array 2 min read numpy.isneginf() in Python The numpy.isneginf() function tests element-wise whether it is negative infinity or not, and returns the result as a boolean array. Syntax :  numpy.isneginf(array, y = None) Parameters : array : [array_like]Input array or object whose elements, we need to test for infinity. y : [array_like]A boole 2 min read numpy.isreal() in Python numpy.isreal(array) : Test element-wise whether it is a real number or not(not infinity or not Not a Number) and return the result as a boolean array. 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