Python3.x Python 2和3之间numpy数组的pickle不兼容

我试图使用以下程序在Python 3.2中加载MNIST dataset linked here:

import pickle
import gzip
import numpy


with gzip.open('mnist.pkl.gz', 'rb') as f:
    l = list(pickle.load(f))
    print(l)

不幸的是，它给了我一个错误:

Traceback (most recent call last):
   File "mnist.py", line 7, in <module>
     train_set, valid_set, test_set = pickle.load(f)
UnicodeDecodeError: 'ascii' codec can't decode byte 0x90 in position 614: ordinal not in range(128)

然后，我try 在Python 2.7中解码pickle文件，并对其重新编码.所以，我用Python 2.7运行了这个程序:

import pickle
import gzip
import numpy


with gzip.open('mnist.pkl.gz', 'rb') as f:
    train_set, valid_set, test_set = pickle.load(f)

    # Printing out the three objects reveals that they are
    # all pairs containing numpy arrays.

    with gzip.open('mnistx.pkl.gz', 'wb') as g:
        pickle.dump(
            (train_set, valid_set, test_set),
            g,
            protocol=2)  # I also tried protocol 0.

它运行时没有出错，所以我用Python 3.2重新运行了这个程序:

import pickle
import gzip
import numpy

# note the filename change
with gzip.open('mnistx.pkl.gz', 'rb') as f:
    l = list(pickle.load(f))
    print(l)

然而，它给了我和以前一样的错误.我怎样才能让它工作？

This is a better approach for loading the MNIST dataset.