How to find an index of the first matching element in TensorFlow

Question

I am looking for a TensorFlow way of implementing something similar to Python\'s list.index() function.

Given a matrix and a value to find, I want to know the first

Answer 1

Looks a little ugly but works (assuming m and val are both tensors):

idx = list()
for t in tf.unpack(m, axis=0):
    idx.append(tf.reduce_min(tf.where(tf.equal(t, val))))
idx = tf.pack(idx, axis=0)

EDIT: As Yaroslav Bulatov mentioned, you could achieve the same result with tf.map_fn:

def index1d(t):
    return tf.reduce_min(tf.where(tf.equal(t, val)))

idx = tf.map_fn(index1d, m, dtype=tf.int64)