Python plot 2D array with black and white cells

Question

I want to plot 2D array of 1's and 0's in Python with black and white cells using pyplot.imshow(). If there is '1' then the cell color should be black and if it's '0' the cell color should be white.

I tried this:

grid = np.zeros((4, 4, 4), int)
choices = np.random.choice(grid.size, 6, replace=False)
grid.ravel()[choices] = 1

plt.imshow(grid, cmap='gray')
plt.show()

This is how the output looks like with this code

Answer 1

If you meant to create a 3-dimensional grid, than you are probably interested in plotting all slices:

import matplotlib.pyplot as plt
import numpy as np

np.random.seed(2020)

grid = np.zeros((4, 4, 4), int)
choices = np.random.choice(grid.size, 6, replace=False)
grid.ravel()[choices] = 1

print(grid)

fig,ax=plt.subplots(2,2,figsize=(6,6))
for i,a in enumerate(ax.flatten()):
    a.imshow(grid[i,:,:], cmap='gray_r',)
    a.set_title(f"slice {i}")
plt.show()

yields:

[[[0 0 0 0]
  [0 0 0 0]
  [0 0 0 0]
  [1 1 0 0]]

 [[0 0 0 0]
  [0 0 0 0]
  [0 0 0 0]
  [0 0 0 0]]

 [[0 0 0 0]
  [0 1 0 0]
  [0 0 1 0]
  [0 0 0 0]]

 [[0 1 0 0]
  [1 0 0 0]
  [0 0 0 0]
  [0 0 0 0]]]

and this image:

If, however, you wanted to plot in 2d, then use:

import matplotlib.pyplot as plt
import numpy as np

np.random.seed(2020)

grid = np.zeros((4, 4), int)
choices = np.random.choice(grid.size, 6, replace=False)
grid.ravel()[choices] = 1

print(grid)
plt.imshow(grid,cmap='gray_r')
plt.show()

yields:

[[0 1 1 0]
 [1 0 0 0]
 [0 1 1 0]
 [1 0 0 0]]