Adjusting gridlines and ticks in matplotlib imshow

Question

I\'m trying to plot a matrix of values and would like to add gridlines to make the boundary between values clearer. Unfortunately, imshow decided to locate the tick marks in the

Answer 1

One can find it easier to use plt.pcolor or plt.pcolormesh:

data = np.random.rand(10, 10)
plt.pcolormesh(data, edgecolors='k', linewidth=2)
ax = plt.gca()
ax.set_aspect('equal')

Though, there are some differences among them and plt.imshow, the most obvious being that the image is swapped by the Y-axis (you can reversed it back easily by adding ax.invert_yaxis() though). For further discussion see here: When to use imshow over pcolormesh?