# Python isnan

The Python isnan function is one of the Python Mathematical functions used to check whether the given value is a valid number or not. If it is Positive or Negative value, then isnan returns False otherwise, True.

The syntax of the isnan in Python Programming Language is

`math.isnan(value)`

## Python isnan example

It is a simple example of isnan function to check whether zero is a valid number or not.

```#Python isnan

import math

print(math.isnan(0))```
``False``

Here, we are using the isnan function on different values of both positive and negative. We have also used math.pi inside this isnan function.

```import math

print(math.isnan(1))

print(math.isnan(0.00))

print(math.isnan(-2))

print(math.isnan(-4.0002))

print(math.isnan(math.pi))```
``````False
False
False
False
False``````

Let me check this Python function against NaN (not a number)

```import math

print(math.isnan(float('NaN')))```

isnan and NaN output

``True``

In this isnan Mathematical function example, we are using the infinity, math.inf, not a number values as the function arguments.

```import math

print(math.isnan(float('NaN')))

print(math.isnan(float('inf')))

print(math.isnan(float('-inf')))

print(math.isnan(math.inf))

print(math.isnan(-math.inf))```