matplotlib: Axis default limits with a Circle patch

Question

Consider the following code:

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.gca()
circle = plt.Circle((0, 0), radius = 0.5)
ax.add_patch(circle)
print(plt.axis())
plt.show()

The default axis limits are printed as:

(0.0, 1.0, 0.0, 1.0)

I am not sure why this is the case. So, I would like to learn why?

PS: I know I can just do plt.axis('scaled') so that I can see the entire circle.

Answer 1

Plotting functions like plot or scatter make use of the function autoscale_view (source). However, add_patch does not call it (source). While this explains why the axes are not scaled automatically in your example, I'm not sure what the underlying design choice was.

• hitzg: Does that answer your question? If not, what exactly is your question?
• user59634: the question is "why" - the part that you are not sure about.
• hitzg: I see. I guess @tcaswell knows the answer
• user59634: @hizg I just tried callling autoscale_view() and it fixes my issue. submitted a PR: github.com/matplotlib/matplotlib/pull/3936
• Ben Usman: Please consider updating the answer with ax.autoscale_view() as a recipe.