MNist loading helper for Python 2.7. For Python 3.x, see https://gist.github.com/akesling/42393ccb868125071fdea77d98a0d2f0

mnist.py

import os
import struct
import numpy as np

"""
MNist loading helper for Python 2.7.

For Python 3.x, see https://gist.github.com/akesling/42393ccb868125071fdea77d98a0d2f0

Loosely inspired by http://abel.ee.ucla.edu/cvxopt/_downloads/mnist.py
which is GPL licensed.
"""

def read(dataset = "training", path = "."):
    """
    Python function for importing the MNIST data set.  It returns an iterator
    of 2-tuples with the first element being the label and the second element
    being a numpy.uint8 2D array of pixel data for the given image.
    """

    if dataset is "training":
        fname_img = os.path.join(path, 'train-images-idx3-ubyte')
        fname_lbl = os.path.join(path, 'train-labels-idx1-ubyte')
    elif dataset is "testing":
        fname_img = os.path.join(path, 't10k-images-idx3-ubyte')
        fname_lbl = os.path.join(path, 't10k-labels-idx1-ubyte')
    else:
        raise ValueError, "dataset must be 'testing' or 'training'"

    # Load everything in some numpy arrays
    with open(fname_lbl, 'rb') as flbl:
        magic, num = struct.unpack(">II", flbl.read(8))
        lbl = np.fromfile(flbl, dtype=np.int8)

    with open(fname_img, 'rb') as fimg:
        magic, num, rows, cols = struct.unpack(">IIII", fimg.read(16))
        img = np.fromfile(fimg, dtype=np.uint8).reshape(len(lbl), rows, cols)

    get_img = lambda idx: (lbl[idx], img[idx])

    # Create an iterator which returns each image in turn
    for i in xrange(len(lbl)):
        yield get_img(i)

def show(image):
    """
    Render a given numpy.uint8 2D array of pixel data.
    """
    from matplotlib import pyplot
    import matplotlib as mpl
    fig = pyplot.figure()
    ax = fig.add_subplot(1,1,1)
    imgplot = ax.imshow(image, cmap=mpl.cm.Greys)
    imgplot.set_interpolation('nearest')
    ax.xaxis.set_ticks_position('top')
    ax.yaxis.set_ticks_position('left')
    pyplot.show()

Just a notice for running under Python 3, you should change those lines:

raise ValueError("dataset must be 'testing' or 'training'") # lineno:24

for i in range(len(lbl)): # lineno:38

this script work well i think, for plotting right digit.

however, this is wired.
seems different loading tools(https://github.com/mnielsen/neural-networks-and-deep-learning/blob/master/src/mnist_loader.py) make result different for me when testing network here(https://github.com/mnielsen/neural-networks-and-deep-learning/blob/master/src/network.py).

I got this error, who can help me? Very Thanks.

raise ValueError, "dataset must be 'testing' or 'training'"

For all those who find this and want something working on Python 3.x, I've created an updated gist: https://gist.github.com/akesling/42393ccb868125071fdea77d98a0d2f0