a = np.ones((2,2))
a[0,0]=a[0,1] = 0
mask = a == 0
a[mask] = np.random.random_sample(a.shape)[mask]
print('new a = ', a)

zeros = tf.zeros(tf.shape(a))
mask = tf.greater(a,zeros)
mask_n = tf.equal(a,zeros)
mask = tf.cast(mask,tf.float32)
mask_n = tf.cast(mask_n,tf.float32
r = tf.random_uniform(tf.shape(a),minval = 0.0,maxval=1.0,dtype=tf.float32)
r_add = tf.multiply(mask_n,r)
targets = tf.add(tf.multiply(mask,a),r_add)