[PYTHON] Reading data with TensorFlow

I tried to decompose the data reading mechanism from a file in TensorFlow as a series of flows. I think that it will be a reference for how to take in the binary image data of CIFAR-10, utilize Queue, and send it to the graph as a tensor in Session.

I found out ・ As stated in the official Reading data, reading from a file is performed in 7 steps. -The reason why FilenameQueue is bitten is to shuffle data and execute processing in multiple threads. ・ The following structure is used

tf.Graph().as_default()

    sess=tf.Session()
    tf.train.start_queue_runners(sess=sess)

    for i in range():
        sess.run([ .. ])
```

 Etc.

 Also, [Try using TensorFlow's Reader class](http://qiita.com/knok/items/2dd15189cbca5f9890c5) explains the most important part of how to handle jpeg images, so please also refer to it. Please refer.


 It is assumed that the data of cifar10 is saved as /tmp/cifar10_data/ .. If you run the following code, the image data will be output as a tensor.
 This script extracts the basic parts of data loading and preprocessing from the large number of functions in the cifar10 tutorial. See cifar10_input.py for more processing.







#### **`tensorflow_experiment3.py`**
```py


#coding:utf-8
#Until the Cifar10 image file is read and converted to a tensor.
import tensorflow as tf


FLAGS = tf.app.flags.FLAGS
tf.app.flags.DEFINE_integer('max_steps', 1,
                            """Number of batches to run.""")
tf.app.flags.DEFINE_integer('batch_size', 128,
                            """Number of images to process in a batch.""")
NUM_EXAMPLES_PER_EPOCH_FOR_TRAIN = 50000



with tf.Graph().as_default(): 
	# 1.List of file names
	filenames = ['/tmp/cifar10_data/cifar-10-batches-bin/data_batch_1.bin',
		'/tmp/cifar10_data/cifar-10-batches-bin/data_batch_2.bin',
        '/tmp/cifar10_data/cifar-10-batches-bin/data_batch_3.bin', 
        '/tmp/cifar10_data/cifar-10-batches-bin/data_batch_4.bin', 
        '/tmp/cifar10_data/cifar-10-batches-bin/data_batch_5.bin']
    # 2.No filename shuffle
    # 3.No epoch limit setting


    # 4.Creating a "filename list" queue
	filename_queue = tf.train.string_input_producer(filenames)


	# 5.Creating a reader that matches the data format
	class CIFAR10Record(object):
		pass
	result = CIFAR10Record()

	label_bytes = 1 
	result.height = 32
	result.width = 32
	result.depth = 3
	image_bytes = result.height * result.width * result.depth
	record_bytes = label_bytes + image_bytes

	reader = tf.FixedLengthRecordReader(record_bytes=record_bytes)

	##Open the file by passing the queue to the reader
	result.key, value = reader.read(filename_queue)


	# 6.decode the data from the read result
	record_bytes = tf.decode_raw(value, tf.uint8)


    # 7.Data shaping
    # 7-1.Basic plastic surgery
	result.label = tf.cast(tf.slice(record_bytes, [0], [label_bytes]), tf.int32)
	depth_major = tf.reshape(tf.slice(record_bytes, [label_bytes], [image_bytes]),
                                [result.depth, result.height, result.width])
	result.uint8image = tf.transpose(depth_major, [1, 2, 0])

	read_input = result
	reshaped_image = tf.cast(read_input.uint8image, tf.float32)
	float_image = reshaped_image

	# 7-2.Preparing to shuffle data
	min_fraction_of_examples_in_queue = 0.4
	min_queue_examples = int(NUM_EXAMPLES_PER_EPOCH_FOR_TRAIN *
                            min_fraction_of_examples_in_queue)
	print ('Filling queue with %d CIFAR images before starting to train. '
            'This will take a few minutes.' % min_queue_examples)

    # 7-3.Creating a batch(With shuffle)
	batch_size = FLAGS.batch_size
	num_preprocess_threads = 16
	images, label_batch = tf.train.shuffle_batch(
	[float_image, read_input.label],
        batch_size=batch_size,
        num_threads=num_preprocess_threads,
        capacity=min_queue_examples + 3 * batch_size,
        min_after_dequeue=min_queue_examples)

	images=images
	labels = tf.reshape(label_batch, [batch_size])


	# 8.Run
	sess = tf.Session()
	tf.train.start_queue_runners(sess=sess)
	for step in xrange(FLAGS.max_steps):
		img_label = sess.run([images, labels])
		print(img_label)
	print("FIN.")
```