Bug summary

The type stub for ErrorbarContainer in lib/matplotlib/container.pyi is incorrect.

It is also inconsistent with the online documentation.

Code for reproduction

from matplotlib import pyplot as plt


fig = plt.figure()
axis = fig.add_subplot(111)

container = axis.errorbar([0, 1, 2], [-0.5, 0.2, 0.3], yerr=[0.01, 0.02, 0.01])
print(container.lines)
for idx, elem in enumerate(container.lines):
    print(f"Element {idx}: {elem} | Type = {type(elem)}")

plt.show()
plt.close()

Actual outcome

Expected outcome

Assuming the type stub is correct:

1. The first element should be a Line2D which is correct
2. The second element should be a Line2D which is incorrect as it is actually an empty tuple
3. The third element should be a LineCollection which is incorrect as it is a tuple containing a single LineCollection.

Additional information

I'm not sure if the type stub was always incorrect or it became incorrect over time however it should be fixed as it causes spurious type checker errors.

Obviously we would need to fix the type stub annotation however I am unsure about the true types as it seems that the return types are dynamic dependent on the input arguments to plt.errorbar.

Operating system

Debian

Matplotlib Version

3.8.4

Matplotlib Backend

QtAgg

Python version

3.12.4

Jupyter version

Not applicable

Installation

conda