Feb 2, 2021
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
    # If no existing axes match, then create a new one.
    if ax is None:
        ax = fig.add_subplot(*args, **kwargs)
    elif kwargs:
        _api.warn_external(f"An Axes with subplot spec {args} already exists. "
                           "The existing Axes will be returned, with all "
                           "keyword arguments ignored.")

    bbox = ax.bbox
    axes_to_delete = []
diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
    with plt.ioff():
        plt.ion()
    assert not mpl.is_interactive()


 def test_subplot_warning():
    ax1 = plt.subplot(2, 1, 1)
    with pytest.warns(UserWarning, match='An Axes with subplot spec '
                                         r'\(2, 1, 1\) already exists'):
        ax2 = plt.subplot(2, 1, 1, polar=True)
    assert ax1 is ax2
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1232,6 +1232,10 @@ def subplot(args, *kwargs):
		# If no existing axes match, then create a new one.
		if ax is None:
		ax = fig.add_subplot(args, *kwargs)
		elif kwargs:
		_api.warn_external(f"An Axes with subplot spec {args} already exists. "
		"The existing Axes will be returned, with all "
		"keyword arguments ignored.")

		bbox = ax.bbox
		axes_to_delete = []
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -153,3 +153,11 @@ def test_nested_ion_ioff():
		with plt.ioff():
		plt.ion()
		assert not mpl.is_interactive()


		def test_subplot_warning():
		ax1 = plt.subplot(2, 1, 1)
		with pytest.warns(UserWarning, match='An Axes with subplot spec '
		r'\(2, 1, 1\) already exists'):
		ax2 = plt.subplot(2, 1, 1, polar=True)
		assert ax1 is ax2