You can do it by setting the aspect of the image manually (or by letting it auto-scale to fill up the extent of the figure).
By default, imshow
sets the aspect of the plot to 1, as this is often what people want for image data.
In your case, you can do something like:
import matplotlib.pyplot as plt
import numpy as np
grid = np.random.random((10,10))
fig, (ax1, ax2, ax3) = plt.subplots(nrows=3, figsize=(6,10))
ax1.imshow(grid, extent=[0,100,0,1])
ax1.set_title('Default')
ax2.imshow(grid, extent=[0,100,0,1], aspect="auto")
ax2.set_title('Auto-scaled Aspect')
ax3.imshow(grid, extent=[0,100,0,1], aspect=100)
ax3.set_title('Manually Set Aspect')
plt.tight_layout()
plt.show()