Check if NaN in Tensorflow

If v is a 0d tensor, you might use tf.where to test and update the value:

import numpy as np

v = tf.constant(np.nan)                  # initialize a variable as nan  ​
v = tf.where(tf.is_nan(v), 0., v)
​
with tf.Session() as sess:    
    print(sess.run(v))

# 0.0

For Tensorflow 2.0

you can you:

import tensorflow as tf

if tf.math.is_nan(v):
    print("v is NaN")

or with numpy

import numpy as np

if np.is_nan(v):
    print("v is NaN")