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GeezerVison is showing github.com — Add type hints for matplotlib.dates module by bandpooja · Pull Request #30126 · matplotlib/matplotlib

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bandpooja commented Jun 1, 2025 •

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PR Summary

This pull request introduces comprehensive type hint stubs (.pyi files) for the matplotlib.dates module.

Why this change is necessary:
By providing explicit type information, this enhancement significantly improves static type checking capabilities for matplotlib.dates. Developers using tools like MyPy, Pyright, or Ruff can now catch potential type-related errors earlier in the development cycle, leading to more robust and maintainable code.

Problem solved:
This PR addresses the current lack of precise type information for matplotlib.dates classes and functions during static analysis. It makes the module's API more explicit and easier for automated type-checking tools to understand and validate.

Implementation reasoning:
The implementation involves adding .pyi files that define the types for the core classes and functions within matplotlib.dates.py. This change directly contributes to Matplotlib's ongoing initiative to expand and improve type hinting coverage across its codebase, fostering better developer experience and code quality.

Closes #29994

PR Checklist

"closes Missing type hints for matplotlib.dates.DateFormatter #29994" is in the body of the PR description to link the related issue
new and changed code is tested
- Note: For type stub additions, "tested" typically means running mypy or similar type checkers to ensure no errors are introduced.

Test Result

mypy, ruff and Pyright with the new dates.pyi

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bandpooja added 2 commits

June 1, 2025 02:53


          adding stub-file for dates module

b5c7c2b


          import and type hint corrections

3a7ac41

github-actions Bot added the topic: date handling label

Jun 1, 2025

bandpooja marked this pull request as draft

June 1, 2025 07:41

bandpooja marked this pull request as ready for review

June 1, 2025 07:42

github-actions Bot reviewed

Jun 1, 2025

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bandpooja added 3 commits

June 1, 2025 03:46


          adding a ruff test pass as well

e485a7d


          passing the pyright test

aee2931


          passing all the tests

e75fe2b

bandpooja mentioned this pull request

Jun 1, 2025

Missing type hints for matplotlib.dates.DateFormatter #29994

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timhoffm reviewed

Jun 2, 2025

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lib/matplotlib/dates.pyi Resolved

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tacaswell added this to the v3.11.0 milestone

Jun 2, 2025


          removing Optional and Union to remain consistent with other pyi files

8a0f20f

QuLogic reviewed

Jun 3, 2025

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I've only done up to the formatters; please correct the default values in the rest.

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          correcting overload for datestr2num

dde90a5

bandpooja commented Jun 10, 2025

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Thanks for the review @QuLogic.

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QuLogic commented Jun 10, 2025

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I've only done up to the formatters; please correct the default values in the rest.

Please handle the rest of these.

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          correcting all the default values

8f448fe

bandpooja commented Jun 10, 2025

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Done thanks again !!
Learning to write .pyi files. 😅

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          ruffdog newline at the end of file

64270ee

melissawm added this to First Time Contributors

Jun 19, 2025

melissawm moved this to Needs review in First Time Contributors

Jun 19, 2025

QuLogic reviewed

Jun 20, 2025

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lib/matplotlib/dates.pyi

		fmt: str

		def __init__(self, fmt: str, tz: str \| datetime.tzinfo \| None = ..., *, usetex: bool \| None = ...) -> None: ...
		def __call__(self, x: float, pos: int \| None = ...) -> str: ...

QuLogic Jun 20, 2025

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This inherits from Formatter, so can be dropped.

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lib/matplotlib/dates.pyi

		zero_formats: Sequence[str] \| None = ...,
		show_offset: bool = ...,
		*, usetex: bool \| None = ...) -> None: ...
		def __call__(self, x: float, pos: int \| None = ...) -> str: ...

QuLogic Jun 20, 2025

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Ditto.

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lib/matplotlib/dates.pyi

		defaultfmt: str = ...,
		*, usetex: bool \| None = ...) -> None: ...
		def _set_locator(self, locator: Locator) -> None: ...
		def __call__(self, x: float, pos: int \| None = ...) -> str: ...

QuLogic Jun 20, 2025

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Ditto.

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lib/matplotlib/dates.pyi

		show_offset: bool = ...,
		*, usetex: bool \| None = ...) -> None: ...
		def __call__(self, x: float, pos: int \| None = ...) -> str: ...
		def format_ticks(self, values: Sequence[float]) -> list[str]: ...

QuLogic Jun 20, 2025

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Also inherited.

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lib/matplotlib/dates.pyi

		def __call__(self, x: float, pos: int \| None = ...) -> str: ...
		def format_ticks(self, values: Sequence[float]) -> list[str]: ...
		def get_offset(self) -> str: ...
		def format_data_short(self, value: float) -> str: ...

QuLogic Jun 20, 2025

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Also inherited.

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lib/matplotlib/dates.pyi

Comment on lines +184 to +185

		@staticmethod
		def axisinfo(unit: datetime.tzinfo \| None, axis: Axis) -> None: ...

QuLogic Jun 20, 2025

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This isn't a static method, and doesn't return None.

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lib/matplotlib/dates.pyi

		@staticmethod
		def axisinfo(unit: datetime.tzinfo \| None, axis: Axis) -> None: ...
		@staticmethod
		def convert(obj: datetime.datetime \| datetime.date \| float \| np.datetime64 \| Sequence[datetime.datetime \| datetime.date \| float \| np.datetime64],

QuLogic Jun 20, 2025

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obj is named value in the source. Also where did float and datetime.date input come from? This goes through date2num which takes datetime.datetime | np.datetime64.

And probably this should be overloaded like date2num.

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lib/matplotlib/dates.pyi

Comment on lines +198 to +199

		@staticmethod
		def axisinfo(unit: datetime.tzinfo \| None, axis: Axis) -> None: ...

QuLogic Jun 20, 2025

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Same as above, isn't static and doesn't return None.

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lib/matplotlib/dates.pyi


		class _SwitchableDateConverter:
		@staticmethod
		def _get_converter() -> "ConciseDateConverter" \| "DateConverter": ...

QuLogic Jun 20, 2025

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Note sure why these are quoted.

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lib/matplotlib/dates.pyi

Comment on lines +205 to +212

		@staticmethod
		def axisinfo(unit: datetime.tzinfo \| None, axis: Axis) -> AxisInfo: ...
		@staticmethod
		def default_units(x: datetime.datetime \| datetime.date \| float \| np.ndarray \| Sequence[datetime.datetime \| datetime.date \| float \| np.datetime64],
		axis: Axis) -> datetime.tzinfo \| None: ...
		@staticmethod
		def convert(value: datetime.datetime \| datetime.date \| float \| np.datetime64 \| Sequence[datetime.datetime \| datetime.date \| float \| np.datetime64],
		unit: datetime.tzinfo \| None, axis: Axis) -> float \| np.ndarray: ...

QuLogic Jun 20, 2025

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None of these are static.

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rcomer mentioned this pull request

Aug 4, 2025

[Bug]: Missing typing for dates.py #26942

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QuLogic mentioned this pull request

Aug 5, 2025

Add type stubs for functions in matplotlib.dates #30385

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dstansby commented Aug 12, 2025

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👋 @bandpooja I accidentally started work on this too at #30385 - are you still interested in finishing off this pull request? If you are, please let us know if you have any questions or can help at all. If not, it would be good to know and we can finish off the work you started :)

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tacaswell modified the milestones: v3.11.0, future releases

Apr 3, 2026

tacaswell marked this pull request as draft

April 3, 2026 20:05

tacaswell commented Apr 3, 2026

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I removed this from 3.11 and marked as draft because it has been quiet.

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github-actions Bot added the status: needs rebase label

Apr 3, 2026

myzhang1029 mentioned this pull request

Jun 6, 2026

Add typing interface file and type hints for backends.backend_pdf #31854

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maaz7409 mentioned this pull request

Oct 16, 2026

BLD: Install the type stub for backends.registry #32481

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Missing type hints for matplotlib.dates.DateFormatter

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bandpooja commented Jun 1, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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bandpooja commented Jun 10, 2025

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dstansby commented Aug 12, 2025

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bandpooja commented Jun 1, 2025 •

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