This PR adds support for horizontal and vertical alignment of tick labels through thetick_params method, addressing issues#13774 and#20644. The implementation allows users to control the alignment of tick labels directly throughtick_params, making it more consistent with other tick label properties and easier to use.

Changes Made

Added new parameters totick_params:
- labelhorizontalalignment: Controls the horizontal alignment of tick labels
- labelverticalalignment: Controls the vertical alignment of tick labels
Added validation for alignment parameters:
- For x-axis:labelhorizontalalignment accepts 'left', 'center', 'right'
- For y-axis:labelverticalalignment accepts 'top', 'center', 'bottom', 'baseline', 'center_baseline'
Added tests intest_axis.py to verify the functionality:
- Testing horizontal and vertical alignment for both x and y axes
- Testing parameter validation
Updated documentation:
- Added new parameters totick_params docstring
- Added documentation inaxis_api.rst
- Added a "What's New" entry intick_label_alignment.rst

Example Usage

importmatplotlib.pyplotaspltfig,ax=plt.subplots()# Set horizontal alignment for x-axis labelsax.tick_params(axis='x',labelhorizontalalignment='right')# Set vertical alignment for y-axis labelsax.tick_params(axis='y',labelverticalalignment='top')

Why is this change necessary?

Currently, users need to iterate over tick labels to set their alignment, which is less convenient than usingtick_params. This change makes the API more consistent and user-friendly by:

Providing a more intuitive way to set tick label alignment
Making the API more consistent with other tick label properties
Reducing the need for manual iteration over tick labels
Following the principle of least astonishment - if a user specifiesax.tick_params(axis="y", horizontalalignment="left"), they would expect it to apply to the y-axis labels

Implementation Details

The implementation:

Adds the new parameters to the_translate_tick_params method inAxis class
Adds parameter validation inset_tick_params method
Implements the alignment setting in the_apply_params method of theTick class
Maintains consistency with existing tick parameter translation system

PR checklist

"closesNo support for horizontal alignment in tick_params? #13774" and "closesadd label alignment to tick_params #20644" are in the body of the PR description
New and changed code is tested
- Addedtest_tick_label_alignment intest_axis.py
Plotting related features are demonstrated in an example
- Added example in PR summary
New Features and API Changes are noted with a directive and release note
- Added new parameters totick_params docstring
- Added documentation for new parameters
Documentation complies with general and docstring guidelines
- Updated docstrings inaxes/_base.py andaxis.py
- Added clear descriptions of new parameters

aydengemz added2 commits

May 4, 2025 18:33

Label Aligment Issuematplotlib#20644with Horizontal Supportmatplot…

e88d92c

…lib#13774

ENH: Add horizontal and vertical alignment support to tick_params

d98961a

github-actionsbot added topic: ticks axis labels topic: axes Documentation: APIfiles in lib/ and doc/api labels

May 4, 2025

github-actionsbot reviewed

May 4, 2025

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fix: lint cleanup in _base.py

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evelyn-lo reviewed

May 5, 2025

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Review Summary:

The pull request adds two new keyword arguments to tick_params: labelhorizontalalignment and labelverticalalignment, allowing users to control the alignment of tick labels. These are especially useful when axis='x' or axis='y', offering better control over label placement for improved readability.

What’s good:

The new parameters are clearly named and consistent with existing style conventions.

Good documentation: The new parameters are described in both the docstring and usage examples.

The update is minimally invasive and leverages the existing tick_params logic.

Temporary storage of the axis parameter in self._tick_params_axis for use in Axis.set_tick_params is a practical way to enable context-aware behavior.

Suggested Improvements:

Validation logic – While _api.check_in_list validates axis, there's no explicit validation of labelhorizontalalignment and labelverticalalignment. Consider checking that these are valid strings ('center', 'left', 'right', etc.) supported by Text.set_horizontalalignment.

Docstring enhancement – You might clarify that these alignment settings only apply if the axis supports tick labels and that both parameters are passed down to Axis.set_tick_params.

Edge case clarification – For axis='both', it's not clear how or whether both alignments are respected (e.g., is labelhorizontalalignment passed to y-axis?).

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rcomer commentedMay 5, 2025

Thank you for the potential contribution. Unfortunately many tests are failing, including the one you added. I also ran your example code with your branch and got this - the label alignment appears to be unaffected, and we see ticks on the top and right spines that should not be there.

Before opening pull requests, you shouldtest changes locally to verify these kind of issue do not come up.

I'm going to mark this as "draft" for now. Please mark it as "ready for review" when you are ready. In the meantime, if you need help, feel free to ask questions here. Or you may prefer to ask them in ourincubator gitter room.

Finally, if you are using AI for any aspect of this, please seehttps://matplotlib.org/devdocs/devel/contribute.html#restrictions-on-generative-ai-usage