Update plot_modifications.py

[tiapac]

I noticed that making a contour plot does not allow me to use the kwarg "cmap" in the 'plot_args' dictionary.
If I add the "cmap" key work to 'plot_args' as in

s = yt.ProjectionPlot(ds, "x", ("gas","density"))	
s.annotate_contour(("gas","density"), plot_args = { "cmap":"jet"})```

returns

Traceback (most recent call last):
  File ".conda/envs/ytenv/lib/python3.12/site-packages/yt/visualization/plot_window.py", line 1285, in run_callbacks
    callback(cbw)
  File ".conda/envs/ytenv/lib/python3.12/site-packages/yt/visualization/plot_modifications.py", line 1032, in __call__
    cset = plot._axes.contour(xi, yi, zi, levels, **self.plot_args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".conda/envs/ytenv/lib/python3.12/site-packages/matplotlib/__init__.py", line 1473, in inner
    return func(
           ^^^^^
  File ".conda/envs/ytenv/lib/python3.12/site-packages/matplotlib/axes/_axes.py", line 6659, in contour
    contours = mcontour.QuadContourSet(self, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".conda/envs/ytenv/lib/python3.12/site-packages/matplotlib/contour.py", line 801, in __init__
    raise ValueError('Either colors or cmap must be None')

ValueError: Either colors or cmap must be None

The cause is that by default yt partially generate said dictionary ( in yt/visualization/plot_modifications.py, line 931 ) and then add the user supplied options:

class ContourCallback(PlotCallback):
...
...
...
    def __init__(
        self,
        field: AnyFieldKey,
        levels: int = 5,
        *,
        factor: tuple[int, int] | int = 4,
        clim: tuple[float, float] | None = None,
        label: bool = False,
        take_log: bool | None = None,
        data_source: YTDataContainer | None = None,
        plot_args: dict[str, Any] | None = None,
        text_args: dict[str, Any] | None = None,
        ncont: int | None = None,  # deprecated
    ) -> None:
...
...
...
self.plot_args = {
    "colors": "black",
    "linestyles": "solid",
    **(plot_args or {}),
}

This generate a conflict in matplotlib because when "colors" is supplied, "cmap" is not accepted.

A solution might be to only add the default values if they are not supplied by the user in plot_args , as also suggested by @chrishavlin .

This is the content of the pull request.

[welcome]

Hi! Welcome, and thanks for opening this pull request. We have some guidelines for new pull requests, and soon you'll hear back about the results of our tests and continuous integration checks. Thank you for your contribution!

[chrishavlin]

@tiapac did you mean to close this one?

[tiapac]

Yes, I modified through the online editor, so I was worried that the indentation was not correct. I also wanted to add a bit of context to the changes for future references. I tested it locally and it's ok, so I'll reopen it.
Sorry, I am still a bit clumsy with git outside my private repositories.

[chrishavlin]

pre-commit.ci autofix

[chrishavlin]

@tiapac I just triggered the pre-commit bot to fix the failing style check: locally you'll want to run git pull to make sure you pull those changes locally.

[tiapac]

The type check test gives an error here:

Run mypy yt
  mypy yt
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.10.16/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/Python/3.10.16/x64/lib/pkgconfig
    Python_ROOT_DIR: /opt/hostedtoolcache/Python/3.10.16/x64
    Python[2](https://github.com/yt-project/yt/actions/runs/13268926486/job/37043480434?pr=5116#step:6:2)_ROOT_DIR: /opt/hostedtoolcache/Python/[3](https://github.com/yt-project/yt/actions/runs/13268926486/job/37043480434?pr=5116#step:6:3).10.16/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/Python/3.10.16/x6[4](https://github.com/yt-project/yt/actions/runs/13268926486/job/37043480434?pr=5116#step:6:4)
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.10.16/x64/lib
yt/visualization/plot_modifications.py: note: In member "__init__" of class "ContourCallback":
yt/visualization/plot_modifications.py:966: error: Unsupported right operand type for in ("dict[str, Any] | None")  [operator]
yt/visualization/plot_modifications.py:968: error: Unsupported right operand type for in ("dict[str, Any] | None")  [operator]
yt/utilities/performance_counters.py: note: In member "print_stats" of class "PerformanceCounters":
yt/utilities/performance_counters.py:73: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
Found 2 errors in 1 file (checked [5](https://github.com/yt-project/yt/actions/runs/13268926486/job/37043480434?pr=5116#step:6:5)16 source files)
Error: Process completed with exit code 1.

I think it is because if plot_args defaults to None, thus the in operation fails in such case.
A solution might be to switch to

if "colors" not in self.plot_args and "cmap" not in self.plot_args: ...
instead of
if "colors" not in plot_args and "cmap" not in plot_args: ... ?

[chrishavlin]

A solution might be to switch to

if "colors" not in self.plot_args and "cmap" not in self.plot_args: ...

yup! that should fix it.