[Matplotlib] plt.subplots(ax = ax.flatten)
ax.flatten(): Transform n*m to 1*nm 1-D Array
fig, ax = plt.subplots(nrows=2,ncols=2,sharex='all',sharey='all')
ax = ax.flatten()

for i in range(4):
img = image[i].reshape(28, 28)
ax[i].imshow(img, cmap='Greys', interpolation='nearest')

# ax[i] is available
Without flatten()
fig, ax = plt.subplots(nrows=2,ncols=2,sharex='all',sharey='all')
for i in range(4):
img = image[i].reshape(28, 28)
ax[0, 0].imshow(img, cmap='Greys', interpolation='nearest')
ax[0, 1].imshow(img, cmap='Greys', interpolation='nearest')
ax[1, 0].imshow(img, cmap='Greys', interpolation='nearest')
ax[1, 1].imshow(img, cmap='Greys', interpolation='nearest')

# ax[i] is unavailable

正确不？