# Check for NaN Values in Python Using math.isnan

> Use the math.isnan function to check whether a float value is NaN in Python, with a robust implementation that handles non-numeric types using try-except

**URL:** https://sentry.io/answers/check-for-nan-values-in-python/

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## The Problem

I sometimes see the value NaN (Not a Number) when working with floats in Python. How can I check whether a given value is NaN?

## The Solution

The best way to do this is by using the [`isnan()`](https://docs.python.org/3/library/math.html#math.isnan) function from Python's built-in [`math`](https://docs.python.org/3/library/math.html) library:

```python
import math

nan = float('nan')
zero = 0
one = 1

print(math.isnan(nan))  # will print True
print(math.isnan(zero))  # will print False
print(math.isnan(one))  # will print False
```

Note that `isnan()` will throw a `TypeError` if given a non-numeric value. Thus, a more robust implementation might look like this:

```python
import math

def is_nan(value):
    try:
        return math.isnan(value)
    except TypeError:
        return False

nan = float('nan')
zero = 0
one = 1
hello = "Hello!"

print(is_nan(nan))  # will print True
print(is_nan(zero))  # will print False
print(is_nan(one))  # will print False
print(is_nan(hello))  # will print False
```

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*Source: [sentry.io/answers/check-for-nan-values-in-python/](https://sentry.io/answers/check-for-nan-values-in-python/)*