使用Dataset API简化了整个过程。(1): Convert numpy array to tfrecords和(2): read the tfrecords to generate batches中的一个或多个。

1.从numpy数组创建tfrecords：

Example arrays:
inputs = np.random.normal(size=(5, 32, 32, 3))
labels = np.random.randint(0,2,size=(5,))

def npy_to_tfrecords(inputs, labels, filename):
  with tf.io.TFRecordWriter(filename) as writer:
    for X, y in zip(inputs, labels):
        # Feature contains a map of string to feature proto objects
        feature = {}
        feature['X'] = tf.train.Feature(float_list=tf.train.FloatList(value=X.flatten()))
        feature['y'] = tf.train.Feature(int64_list=tf.train.Int64List(value=[y]))

        # Construct the Example proto object
        example = tf.train.Example(features=tf.train.Features(feature=feature))

        # Serialize the example to a string
        serialized = example.SerializeToString()

        # write the serialized objec to the disk
        writer.write(serialized)

npy_to_tfrecords(inputs, labels, 'numpy.tfrecord')

2.使用数据集API读取tf记录：

filenames = ['numpy.tfrecord']
dataset = tf.data.TFRecordDataset(filenames)
# for version 1.5 and above use tf.data.TFRecordDataset

# example proto decode
def _parse_function(example_proto):
    keys_to_features = {'X':tf.io.FixedLenFeature(shape=(32, 32, 3), dtype=tf.float32),
                      'y': tf.io.FixedLenFeature((), tf.int64, default_value=0)}
    parsed_features = tf.io.parse_single_example(example_proto, keys_to_features)
    return parsed_features['X'], parsed_features['y']

# Parse the record into tensors.
dataset = dataset.map(_parse_function)  
  
# Generate batches
dataset = dataset.batch(5)

检查生成的批是否正确：

for data in dataset:
    break
np.testing.assert_allclose(inputs[0] ,data[0][0])
np.testing.assert_allclose(labels[0] ,data[1][0])