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# Python math library | isnan() method

Python has math library and has many functions regarding it. One such function is isnan(). This method is used to check whether a given parameter is a valid number or not.

Syntax : math.isnan(x) Parameters : x [Required] : It is any valid python data type or any number. Returns: Return type is boolean. -> Returns False if the given parameter is any number(positive or negative) -> Returns True if given parameter is NaN (Not a Number).

Time Complexity: O(1)

Auxiliary Space: O(1)

Code #1:

## python3

 `# Python3 code to demonstrate``# the working of isnan()``import` `math` `# initializing the value``test_int ``=` `4``test_neg_int ``=` `-``3``test_float ``=` `0.00` `# checking isnan() values``# with different numbers``print` `(math.isnan(test_int))``print` `(math.isnan(test_neg_int))``print` `(math.isnan(test_float))`

Output:

```False
False
False```

Code #2:

## python3

 `# Python3 code to demonstrate``# the working of isnan()``import` `math` `# checking isnan() values``# with inbuilt numbers``print` `(math.isnan(math.pi))``print` `(math.isnan(math.e))`  `# checking for NaN value``print` `(math.isnan(``float``(``'nan'``)))`

Output:

```False
False
True```
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