Examples of how to check if a number is NAN or INF in python### Vérifier si un nombre est égale à 'NAN'

### Check if a number is 'NAN'

To check if a number is 'NAN', a solution is to use the math module with the function isnan()

`import numpy as np`

`import math`

`x = 2.0`

`math.isnan(x)`

gives

`False`

while

`x = np.nan`

`math.isnan(x)`

returns

`True`

### Check if a number is 'INF'

To check if a number is 'INF', a solution is to use the math module with the function isinf()

`import numpy as np`

`import math`

`x = 2.0`

`math.isinf(x)`

gives

`False`

while

`x = np.inf`

`math.isinf(x)`

returns

`True`

### Check if a number is finite

Another solution, it is possible to check if a number is finite with the function isfinite()

`>>> import numpy as np`

`>>> x = np.nan`

`>>> y = np.inf`

`>>> x`

`nan`

`>>> y`

`inf`

`>>> np.isfinite(x)`

`False`

`>>> np.isfinite(y)`

`False`

### Check is a variable is a number with isinstance

To check if a variable is a number (int or float for example) a solution is to use isinstance:

`x = 1.2`

`isinstance(x, (int, float))`

gives here

`True`

while

`x = 'abcd'`

`isinstance(x, (int, float))`

returns

` false`