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[Bug]: Mypy not finding the right return type for ax.subplots(...,projection="3d") #27455
Closed as not planned
Description
Bug summary
Mypy says that an ax created by ax = fig.add_subplot(..., projection="3d") is type Axes rather than the expected Axes3D. This causes type checking Axes3D methods to fail e.g. ax.plot_surface(). Maybe this is fixed if/when mpl_toolkits gets typing stubs?
Code for reproduction
import numpy as np
from matplotlib import pyplot as plt
# Demo data
x, y = np.meshgrid(np.linspace(-5, 5, 100), np.linspace(-5, 5, 100))
z = np.sqrt(x**2 + y**2)
fig = plt.figure()
ax = fig.add_subplot(1, 2, 1, projection="3d")
reveal_type(ax) # matplotlib.axes._axes.Axes
ax.plot_surface(x, y, z) # mypy error: "Axes" has no attribute "plot_surface" [attr-defined]
plt.show()Actual outcome
python3.9 -m mypy demo.py produces:
demo.py:10: note: Revealed type is "matplotlib.axes._axes.Axes"
demo.py:11: error: "Axes" has no attribute "plot_surface" [attr-defined]
Found 1 error in 1 file (checked 1 source file)
Expected outcome
Expected no attr-defined mypy error for calling ax.surface() on an Axes3D`
demo.py:10: note: Revealed type is "mpl_toolkits.mplot3d.axes3d.Axes3D"
Additional information
This occurs with the latest mypy (1.7.1)
Operating system
Ubuntu 20.04
Matplotlib Version
3.8.2
Matplotlib Backend
TKAgg
Python version
Python 3.9.5
Jupyter version
No response
Installation
pip
Activity
ksunden commentedon Dec 6, 2023
None of the 3d code (or anything else in
mpl_toolkits) is type hinted yet, and while we may be able to do the built in projections at least, the projection argument is a very dynamic field which is hard for static type hinting (e.g. you can register your own projections, but there is no way to tell the type checker about them)In at least the short term, if you know better than the type system, there are cases where you may wish to use
typing.castto inform the type checker.jmdelaney8 commentedon Dec 6, 2023
I figured this might be the case, but wanted to flag just to be sure. I appreciate the quick response!
tacaswell commentedon Dec 7, 2023
I'm going to close this as "can't fix" as we are pushing the limits of what a static type checker can do on top of our full leveraging of the dynamicness of Python.
timhoffm commentedon Oct 21, 2024
I you really need to placate static type checkers, you could do
Jeitan commentedon Dec 17, 2024
@timhoffm Is there anything special you did to make that cast work, or a version limitation? I have just tried to do the exact same thing and Mypy is not recognizing the cast at all. Nothing changes in its output whether the cast is there or not. Python 3.11, matplotlib 3.9.3, mypy 1.13.
QuLogic commentedon Dec 17, 2024
I think the problem is that no toolkits have typing, so casting to an
Axes3Ddoes nothing for mypy; it just becomesAny.Jeitan commentedon Dec 17, 2024
@QuLogic Ah, that would explain it, thank you! Ugh. I recently upgraded a bunch of versions of things and suddenly I have all these typing errors. I guess I'll just have to turn typing off through the problematic code.