Jun 29, 2020 · Jun 26, 2020
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
    matplotlib.get_backend
    """
    name = validate_backend(backend)
    # we need to use the base-class method here to avoid (prematurely)
    # resolving the "auto" backend setting
    if dict.__getitem__(rcParams, 'backend') == name:
        # Nothing to do if the requested backend is already set
        pass
    else:
        try:
            from matplotlib import pyplot as plt
            plt.switch_backend(name)
        except ImportError:
            if force:
                raise
        # if pyplot is not already imported, do not import it.  Doing
        # so may trigger a `plt.switch_backend` to the _default_ backend
        # before we get a chance to change to the one the user just requested
        plt = sys.modules.get('matplotlib.pyplot')
        # if pyplot is imported, then try to change backends
        if plt is not None:
            try:
                # we need this import check here to re-raise if the
                # user does not have the libraries to support their
                # chosen backend installed.
                plt.switch_backend(name)
            except ImportError:
                if force:
                    raise
        # if we have not imported pyplot, then we can set the rcParam
        # value which will be respected when the user finally imports
        # pyplot
        else:
            rcParams['backend'] = backend
    # if the user has asked for a given backend, do not helpfully
    # fallback
    rcParams['backend_fallback'] = False


 if os.environ.get('MPLBACKEND'):
diff --git a/lib/matplotlib/tests/test_rcparams.py b/lib/matplotlib/tests/test_rcparams.py
    with pytest.raises(subprocess.CalledProcessError):
        subprocess.run(
            [sys.executable, "-c",
             "import matplotlib; matplotlib.use('tkagg')"],
             ("import matplotlib;" +
              "matplotlib.use('tkagg');" +
              "import matplotlib.pyplot")
             ],
            env=env, check=True)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1136,16 +1136,34 @@ def use(backend, *, force=True):
		matplotlib.get_backend
		"""
		name = validate_backend(backend)
		# we need to use the base-class method here to avoid (prematurely)
		# resolving the "auto" backend setting
		if dict.__getitem__(rcParams, 'backend') == name:
		# Nothing to do if the requested backend is already set
		pass
		else:
		try:
		from matplotlib import pyplot as plt
		plt.switch_backend(name)
		except ImportError:
		if force:
		raise
		# if pyplot is not already imported, do not import it. Doing
		# so may trigger a `plt.switch_backend` to the _default_ backend
		# before we get a chance to change to the one the user just requested
		plt = sys.modules.get('matplotlib.pyplot')
		# if pyplot is imported, then try to change backends
		if plt is not None:
		try:
		# we need this import check here to re-raise if the
		# user does not have the libraries to support their
		# chosen backend installed.
		plt.switch_backend(name)
		except ImportError:
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		if force:
		raise
		# if we have not imported pyplot, then we can set the rcParam
		# value which will be respected when the user finally imports
		# pyplot
		else:
		rcParams['backend'] = backend
		# if the user has asked for a given backend, do not helpfully
		# fallback
		rcParams['backend_fallback'] = False


		if os.environ.get('MPLBACKEND'):
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -473,7 +473,10 @@ def test_backend_fallback_headless(tmpdir):
		with pytest.raises(subprocess.CalledProcessError):
		subprocess.run(
		[sys.executable, "-c",
		"import matplotlib; matplotlib.use('tkagg')"],
		("import matplotlib;" +
		"matplotlib.use('tkagg');" +
		"import matplotlib.pyplot")
		],
		env=env, check=True)


Expand Down