BUG: MatplotlibDeprecationWarning: The is_first_col function was deprecated in Matplotlib 3.4

[arnaujc91]

import pandas as pd
from matplotlib import pyplot as plt

series = [pd.Series([1,2,3,4]) for _ in range(4)]

nrow, ncol = 2, 2
fig, axes = plt.subplots(nrow, ncol)
axes = axes.reshape(-1)
for i, s in enumerate(series):
    s.plot(ax=axes[i])

plt.tight_layout()

Problem description

After executing the previous code the following message from Matplotlib is shown:

The is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.
  if ax.is_first_col():

[lithomas1]

Hi @arnaujc91,
Thanks for the bug report. I can confirm that this happens with the latest matplotlib, and I've spotted some failing tests in our CI related to this.
e.g. https://github.com/pandas-dev/pandas/pull/40713/checks?check_run_id=2240746140

______________ TestDataFramePlotsSubplots.test_subplots_warnings _______________
[gw1] linux -- Python 3.8.8 /home/runner/miniconda3/envs/pandas-dev/bin/python

self = <pandas.tests.plotting.frame.test_frame_subplots.TestDataFramePlotsSubplots object at 0x7f8d83a6edf0>

    def test_subplots_warnings(self):
        # GH 9464
        with tm.assert_produces_warning(None):
            df = DataFrame(np.random.randn(100, 4))
            df.plot(subplots=True, layout=(3, 2))
    
            df = DataFrame(
                np.random.randn(100, 4), index=date_range("1/1/2000", periods=100)
            )
>           df.plot(subplots=True, layout=(3, 2))

pandas/tests/plotting/frame/test_frame_subplots.py:264: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../../miniconda3/envs/pandas-dev/lib/python3.8/contextlib.py:120: in __exit__
    next(self.gen)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    def _assert_caught_no_extra_warnings(
        *,
        caught_warnings: Sequence[warnings.WarningMessage],
Warning: xpected_warning: Optional[Union[Type[Warning], bool]],
    ) -> None:
        """Assert that no extra warnings apart from the expected ones are caught."""
        extra_warnings = []
    
        for actual_warning in caught_warnings:
            if _is_unexpected_warning(actual_warning, expected_warning):
                extra_warnings.append(
                    (
                        actual_warning.category.__name__,
                        actual_warning.message,
                        actual_warning.filename,
                        actual_warning.lineno,
                    )
                )
    
        if extra_warnings:
>           raise AssertionError(f"Caused unexpected warning(s): {repr(extra_warnings)}")
E           AssertionError: Caused unexpected warning(s): [('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426)]

pandas/_testing/_warnings.py:155: AssertionError
______________________ TestDataFramePlots.test_pie_df_nan ______________________
[gw0] linux -- Python 3.8.8 /home/runner/miniconda3/envs/pandas-dev/bin/python

self = <pandas.tests.plotting.frame.test_frame.TestDataFramePlots object at 0x7f65e95a4fd0>

    def test_pie_df_nan(self):
        import matplotlib as mpl
    
        df = DataFrame(np.random.rand(4, 4))
        for i in range(4):
            df.iloc[i, i] = np.nan
        fig, axes = self.plt.subplots(ncols=4)
    
        # GH 37668
        kwargs = {}
        if mpl.__version__ >= "3.3":
            kwargs = {"normalize": True}
    
        with tm.assert_produces_warning(None):
>           df.plot.pie(subplots=True, ax=axes, legend=True, **kwargs)

pandas/tests/plotting/frame/test_frame.py:1523: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../../miniconda3/envs/pandas-dev/lib/python3.8/contextlib.py:120: in __exit__
    next(self.gen)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    def _assert_caught_no_extra_warnings(
        *,
        caught_warnings: Sequence[warnings.WarningMessage],
Warning: xpected_warning: Optional[Union[Type[Warning], bool]],
    ) -> None:
        """Assert that no extra warnings apart from the expected ones are caught."""
        extra_warnings = []
    
        for actual_warning in caught_warnings:
            if _is_unexpected_warning(actual_warning, expected_warning):
                extra_warnings.append(
                    (
                        actual_warning.category.__name__,
                        actual_warning.message,
                        actual_warning.filename,
                        actual_warning.lineno,
                    )
                )
    
        if extra_warnings:
>           raise AssertionError(f"Caused unexpected warning(s): {repr(extra_warnings)}")
E           AssertionError: Caused unexpected warning(s): [('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426), ('MatplotlibDeprecationWarning', MatplotlibDeprecationWarning('\nThe is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead.'), '/home/runner/work/pandas/pandas/pandas/plotting/_matplotlib/tools.py', 426)]

pandas/_testing/_warnings.py:155: AssertionError

The culprit seems to be here.

pandas/pandas/plotting/_matplotlib/tools.py

Line 426 in d01561f

if ax.is_first_col():

[arnaujc91]

Indeed, I just changed this line of code in my local version of Pandas and everything seems to work well. I will try to create a PR tomorrow when I have more time.

Thank you!

[arnaujc91]

Hi @lithomas1,
I tried to create a PR but it seems one test is doing something odd.

=================================== FAILURES ===================================
_________________ TestDataFramePlots.test_plot_scatter_with_c __________________
[gw0] linux -- Python 3.8.8 /usr/share/miniconda/envs/pandas-dev/bin/python

self = <pandas.tests.plotting.frame.test_frame.TestDataFramePlots object at 0x7f955b4d8c40>

    def test_plot_scatter_with_c(self):
        df = DataFrame(
            np.random.randn(6, 4),
            index=list(string.ascii_letters[:6]),
            columns=["x", "y", "z", "four"],
        )
    
        axes = [df.plot.scatter(x="x", y="y", c="z"), df.plot.scatter(x=0, y=1, c=2)]
        for ax in axes:
            # default to Greys
            assert ax.collections[0].cmap.name == "Greys"
    
            # n.b. there appears to be no public method
            # to get the colorbar label
>           assert ax.collections[0].colorbar._label == "z"
E           AttributeError: 'Colorbar' object has no attribute '_label'

pandas/tests/plotting/frame/test_frame.py:763: AttributeError

it is an error which belongs to the test, not to anything I have changed in particular. So I assume it should fail for any PR.

[attack68]

        # n.b. there appears to be no public method
        # to get the colorbar label

      assert ax.collections[0].colorbar._label == "z"

E AttributeError: 'Colorbar' object has no attribute '_label'

recent matplotlib docs seem to suggest there is now a public attribute label, perhaps remove the _ and try again?

[arnaujc91]

Hi @jreback and @attack68,

I think the issue can be solved replacing

assert ax.collections[0].colorbar._label == "z"

with

assert ax.collections[0].colorbar.ax.get_ylabel() == "z" or ax.collections[0].colorbar.ax.get_xlabel() == "z"

This worked for me. As you can see in the original code from colorbar (set_label method):

### More code from the original function 'set_label" ###
        if self.orientation == "vertical":
            self.ax.set_ylabel(label, loc=loc, **kwargs)
        else:
            self.ax.set_xlabel(label, loc=loc, **kwargs)
        self.stale = True

the label to be checked depends on this self.orientation. It seems there is no label attribute.