Why plt imshow doesn t display the image

Question

I am a newbie to keras  and when I tried to run my first keras program on my linux  something just didn t go as I wish  Here is my python code   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     The last sentence doesn t display anything  I copied those codes from a tutorial with out any modification  And there is nothing wrong with the backend of matplotlib on my computer  I have tested that through the code below   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     And then I got a image like that     Moreover  I can get X train 0  printed and it seems nothing wrong  So what could be the reason for that  Why the imshow   function in my first code didn t display anything

User · Answer

If you want to print the picture using imshow   you also execute plt show

User · Answer

The solution was as simple as adding plt show   at the end of the code snippet   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

User · Answer

plt imshow just finishes drawing a picture instead of printing it  If you want to print the picture  you just need to add plt show

User · Answer

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

[python] Why plt.imshow() doesn't display the image?

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