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# Python isnan() Function Example | Python Math Methods

Python isnan() is an inbuilt math function that is used to check whether a given input is a valid number or not. The isnan() function is under the math library, so to use this function, we first have to import the isnan() function.

## Python isnan()

Content Overview

The isnan() function is used to determine whether the given parameter is a valid number or not. If given number x as a parameter is a valid Python number (Positive or Negative), isnan() function returns False.

### Syntax

`math.isnan(x)`

The math.isnan() function takes only one parameter x that is any valid data type in python.

### Return Value

The isnan() function returns two types of value:

True: If the given parameter is not a number

False: If the given parameter is a number

### Programming Examples

See the following code.

```# app.py

# Importing math library
import math

# Checking working of isnan()

# When the number is integer
print(math.isnan(15))
# When the number is float
print(math.isnan(14.55))
# When the number is negative
print(math.isnan(-34))
# When the number is not finite
print(math.isnan(float('nan')))
```

#### Output

```False
False
False
True```

In this program, we have imported the math library, and then we have checked the output of the isnan() function using various input.

We have checked output for integer, float, and negative numbers, respectively; for all these cases, the output is False. Then we have checked output for nan, here the output is True because nan is not a number.

Let’s see another example.

```# app.py

import math

# checking isnan() values
print(math.isnan(math.pi))
print(math.isnan(math.e))
```

#### Output

```python3 app.py
False
False```

## Conclusion

If you want to check for NaN values in Python, then use the Python isnan() function provided by the math library.

Finally, Python isnan() Function Example is over.