TensorFlow: does tf.train.batch automatically load the next batch when the batch has finished training?

You should call sess.run(...) again to load a new batch.

The tf.train.batch(..) will always load batch_size tensors. For example 100 images and a batch_size=30, then you will have 3*30 batches as in you can call sess.run(batch) three times before the input queue will start from the beginning (or stop if epoch=1).

This means that you miss out on 100-3*30=10 samples from training. In case you do not want to miss them you can do tf.train.batch so now you will have 3x 30-sample-batches and 1x 10-sample-batch before the input queue will restart.

For example:

queue = tf.train.string_input_producer(filenames,
        num_epochs=1) # only iterate through all samples in dataset once
reader = tf.TFRecordReader() 
example = reader.read(queue)
image, label = your_conversion_fn(example)
# batch will now load up to 100 image-label-pairs on sess.run(...)
# most tf ops are tuned to work on batches
# this is faster and also gives better result on e.g. gradient calculation
batch = tf.train.batch([image, label], batch_size=100)
with tf.Session() as sess:
# "boilerplate" code
    sess.run([
        tf.local_variables_initializer(),
        tf.global_variables_initializer(),
    ])
    coord = tf.train.Coordinator()
    threads = tf.train.start_queue_runners(sess=sess, coord=coord)
    try:
# in most cases coord.should_stop() will return True
# when there are no more samples to read
# if num_epochs=0 then it will run for ever
        while not coord.should_stop():
# will start reading, working data from input queue
# and "fetch" the results of the computation graph
# into raw_images and raw_labels
            raw_images, raw_labels = sess.run([images, labels])
    finally:
        coord.request_stop()
        coord.join(threads)