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

You can shift the pixels by passing the extent argument to imshow. extent is a 4-element list of scalars (left, right, bottom, top):

foo = np.random.rand(35).reshape(5, 7)
# This keeps the default orientation (origin at top left):
extent = (0, foo.shape[1], foo.shape[0], 0)
_, ax = plt.subplots()
ax.imshow(foo, extent=extent)
ax.grid(color='w', linewidth=2)
ax.set_frame_on(False)