Different Readers for different file types（Tensorflow 的几种读取数据的方式）

tf.TextLineReader
Outputs the lines of a file delimited by newlines
E.g. text files, CSV files

tf.FixedLengthRecordReader
Outputs the entire file when all files have same fixed lengths
E.g. each MNIST file has 28 x 28 pixels, CIFAR-10 32 x 32 x 3

tf.WholeFileReader
Outputs the entire file content

tf.TFRecordReader
Reads samples from TensorFlow’s own binary format (TFRecord)