为什么 plt.imshow()不显示图像？

我是 keras 的新手，当我尝试在 Linux 上运行我的第一个 keras 程序时，有些事情并没有如我所愿。下面是我的 Python 代码:

import numpy as np
np.random.seed(123)
from keras.models import Sequential
from keras.layers import Dense, Dropout, Activation, Flatten
from keras.layers import Convolution2D, MaxPooling2D
from keras.utils import np_utils
from keras.datasets import mnist
(X_train,y_train),(X_test,y_test) = mnist.load_data()
print X_train.shape
from matplotlib import pyplot as plt
plt.imshow(X_train[0])

最后一句什么也没说。我从教程中复制了这些代码，没有做任何修改。在我的电脑上，matplotlib 的后端没有任何问题。我已经通过下面的代码对其进行了测试。

import matplotlib.pyplot as plt


data = [[0, 0.25], [0.5, 0.75]]


fig, ax = plt.subplots()
im = ax.imshow(data, cmap=plt.get_cmap('hot'), interpolation='nearest',
vmin=0, vmax=1)
fig.colorbar(im)
plt.show()

然后我就想到了这样一幅画面:

此外，我可以得到 X _ train [0]打印，似乎没有什么问题。
那么原因是什么呢? 为什么在我的第一个代码中的 imshow ()函数没有显示任何东西？

221650

import numpy as np np.random.seed(123) from keras.models import Sequential from keras.layers import Dense, Dropout, Activation, Flatten from keras.layers import Convolution2D, MaxPooling2D from keras.utils import np_utils from keras.datasets import mnist (X_train,y_train),(X_test,y_test) = mnist.load_data() print X_train.shape from matplotlib import pyplot as plt plt.imshow(X_train[0]) plt.show()

小开

plt.imshow displays the image on the axes, but if you need to display multiple images you use show() to finish the figure. The next example shows two figures:

import numpy as np
from keras.datasets import mnist
(X_train,y_train),(X_test,y_test) = mnist.load_data()
from matplotlib import pyplot as plt
plt.imshow(X_train[0])
plt.show()
plt.imshow(X_train[1])
plt.show()

In Google Colab, if you comment out the show() method from previous example just a single image will display (the later one connected with X_train[1]).

Here is the content from the help:

plt.show(*args, **kw)
Display a figure.
When running in ipython with its pylab mode, display all
figures and return to the ipython prompt.


In non-interactive mode, display all figures and block until
the figures have been closed; in interactive mode it has no
effect unless figures were created prior to a change from
non-interactive to interactive mode (not recommended).  In
that case it displays the figures but does not block.


A single experimental keyword argument, *block*, may be
set to True or False to override the blocking behavior
described above.






plt.imshow(X, cmap=None, norm=None, aspect=None, interpolation=None, alpha=None, vmin=None, vmax=None, origin=None, extent=None, shape=None, filternorm=1, filterrad=4.0, imlim=None, resample=None, url=None, hold=None, data=None, **kwargs)
Display an image on the axes.


Parameters
----------
X : array_like, shape (n, m) or (n, m, 3) or (n, m, 4)
Display the image in `X` to current axes.  `X` may be an
array or a PIL image. If `X` is an array, it
can have the following shapes and types:


- MxN -- values to be mapped (float or int)
- MxNx3 -- RGB (float or uint8)
- MxNx4 -- RGBA (float or uint8)


The value for each component of MxNx3 and MxNx4 float arrays
should be in the range 0.0 to 1.0. MxN arrays are mapped
to colors based on the `norm` (mapping scalar to scalar)
and the `cmap` (mapping the normed scalar to a color).