Improving error message for width and position type mismatch in violinplot#30752
Merged
rcomer merged 16 commits intomatplotlib:mainfrom Jan 25, 2026
Merged
Improving error message for width and position type mismatch in violinplot#30752rcomer merged 16 commits intomatplotlib:mainfrom
rcomer merged 16 commits intomatplotlib:mainfrom
Conversation
timhoffm
reviewed
Nov 16, 2025
timhoffm
reviewed
Nov 17, 2025
Contributor
There was a problem hiding this comment.
Pull request overview
This PR improves error messaging in the violin method to provide clearer feedback when datetime-like position arguments are used with incompatible float width values. The changes add validation that checks type compatibility between positions and widths, raising a TypeError with a helpful message before the cryptic type operation error would occur during arithmetic operations.
Key changes:
- Added datetime import to
lib/matplotlib/axes/_axes.py - Implemented validation logic to detect datetime/date or np.datetime64 positions paired with non-timedelta widths
- Added comprehensive test coverage for the error cases and normal numeric position usage
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 11 comments.
| File | Description |
|---|---|
| lib/matplotlib/axes/_axes.py | Added datetime import and validation logic to check position/width type compatibility before arithmetic operations |
| lib/matplotlib/tests/test_axes.py | Added test helper function and 5 test cases covering datetime64, datetime, scalar widths, mixed positions, and numeric positions |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Member
|
From a quick check, AI comments mostly make sense. @hasanrashid please act on them. |
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
…alidation - Improve pytest match strings with proper line continuation formatting - Enhanced error messages provide clear examples for correct usage
timhoffm
reviewed
Dec 21, 2025
lib/matplotlib/axes/_axes.py
Outdated
Comment on lines
+9036
to
+9038
| return {key: [] for key in [ | ||
| 'bodies', 'cmeans', 'cmins', 'cmaxes', 'cbars', | ||
| 'cmedians', 'cquantiles']} |
Member
There was a problem hiding this comment.
This is not correct. So far:
In [3]: ax.violin([])
Out[3]:
{'bodies': [],
'cmaxes': <matplotlib.collections.LineCollection at 0x787bf23cb080>,
'cmins': <matplotlib.collections.LineCollection at 0x787be8142ea0>,
'cbars': <matplotlib.collections.LineCollection at 0x787be821f9e0>}While early returns are usually good, I wouldn't do it in this case as you'd have to exactly figure out how to construct the complex return type. Just let it fall through as before
Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
timhoffm
reviewed
Dec 21, 2025
Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
timhoffm
approved these changes
Dec 22, 2025
Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
rcomer
approved these changes
Jan 25, 2026
Member
rcomer
left a comment
rcomer
left a comment
There was a problem hiding this comment.
Thanks @hasanrashid and sorry it took me a while to get back to this.
llohse
pushed a commit
to llohse/matplotlib
that referenced
this pull request
Feb 3, 2026
…inplot (matplotlib#30752) * Improving error message for width and position type mismatch in violinplot * Improving error message for width and position type mismatch in violinplot * Fix violin plot statistics in test data * Trigger CI pipeline * Trigger CI pipeline * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/tests/test_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Store original widths parameter before conversion for accurate type validation - Improve pytest match strings with proper line continuation formatting - Enhanced error messages provide clear examples for correct usage * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Remove low-information comment Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> Co-authored-by: Ruth Comer <10599679+rcomer@users.noreply.github.com>
llohse
pushed a commit
to llohse/matplotlib
that referenced
this pull request
Feb 3, 2026
…inplot (matplotlib#30752) * Improving error message for width and position type mismatch in violinplot * Improving error message for width and position type mismatch in violinplot * Fix violin plot statistics in test data * Trigger CI pipeline * Trigger CI pipeline * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/tests/test_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Store original widths parameter before conversion for accurate type validation - Improve pytest match strings with proper line continuation formatting - Enhanced error messages provide clear examples for correct usage * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Remove low-information comment Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> Co-authored-by: Ruth Comer <10599679+rcomer@users.noreply.github.com>
llohse
pushed a commit
to llohse/matplotlib
that referenced
this pull request
Feb 3, 2026
…inplot (matplotlib#30752) * Improving error message for width and position type mismatch in violinplot * Improving error message for width and position type mismatch in violinplot * Fix violin plot statistics in test data * Trigger CI pipeline * Trigger CI pipeline * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update lib/matplotlib/tests/test_axes.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Store original widths parameter before conversion for accurate type validation - Improve pytest match strings with proper line continuation formatting - Enhanced error messages provide clear examples for correct usage * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Update lib/matplotlib/axes/_axes.py Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> * Remove low-information comment Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com> Co-authored-by: Ruth Comer <10599679+rcomer@users.noreply.github.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR intends to close [ENH]: Support using datetimes as positions argument to violin(...) #30417
It should be possible to set the position of a violin plot to be a datetime. Currently, an attempt to do this results in this error message: TypeError: unsupported operand type(s) for +: 'float' and 'datetime.datetime'
The error stems from trying to perform operations between float and datetime if datetime was provided as position arguments.
The proposed solution improves the error message to be:
"If positions are datetime/date values, pass widths as datetime.timedelta (e.g., datetime.timedelta(days=10)) or numpy.timedelta64.
unit tests are in tests\test_violinplot_datetime.py
I had opened another PR #30545, but messed up the commits while making changes. I am making this one after reading the suggestion here: #30508 (comment) by @rcomer . This change updates the error message instead of converting the position and width