How to check if a number is NAN or INF in python ?

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

References

• numpy.isfinite
• math — Mathematical functions
• How to check for NaN in python?
• python nan and inf values
• Assigning a variable NaN in python without numpy
• Fast check for NaN in NumPy