>>> import tensorflow as tf
>>> state = tf.Variable(0, name='counter')
>>> one = tf.constant(1)
>>> new_value = tf.add(state, one)
>>> update = tf.assign(state, new_value)
>>> init = tf.global_variables_initializer()
>>>
>>> with tf.Session() as sess:
... sess.run(init)
... for _ in range(3):
... sess.run(update)
... print(sess.run(state))
1
1
2
2
3
3