# numpy.isnan() in Python

numpy.isnan(array [, out]) : Test element-wise whether it is NaN or not return the result as a boolean array.
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 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 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-ID. Please run them on your systems to explore the working.
.
This article is contributed by Mohit Gupta_OMG 😀. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

My Personal Notes arrow_drop_up

Improved By : Akanksha_Rai

Article Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.