How to get the count of an element in a tensor in TensorFlow?

Question

I want to get the count of an element in a tensor, for example, t = [1, 2, 0, 0, 0, 0] (t is a tensor). I can get the amount 4 of zeros by calling t.count(0) in Python, but in TensorFlow, I can't find any functions to do this. How can I get the count of zeros?

Answer 1

There isn't a built in count method in TensorFlow right now. But you could do it using the existing tools in a method like so:

def tf_count(t, val):
    elements_equal_to_value = tf.equal(t, val)
    as_ints = tf.cast(elements_equal_to_value, tf.int32)
    count = tf.reduce_sum(as_ints)
    return count

Answer 2

To count just a specific element you can create a boolean mask, convert it to int and sum it up:

import tensorflow as tf

X = tf.constant([6, 3, 3, 3, 0, 1, 3, 6, 7])
res = tf.reduce_sum(tf.cast(tf.equal(X, 3), tf.int32))
with tf.Session() as sess:
    print sess.run(res)

Also you can count every element in the list/tensor using tf.unique_with_counts;

import tensorflow as tf

X = tf.constant([6, 3, 3, 3, 0, 1, 3, 6, 7])
y, idx, cnts = tf.unique_with_counts(X)
with tf.Session() as sess:
    a, _, b = sess.run([y, idx, cnts])
    print a
    print b