Backport PR #12608: ENH: allow matplotlib.use after getbackend

tacaswell · MeeseeksDev[bot] · commit 44b8bf7eb80f · 2018-10-29T19:16:39.000Z
diff --git a/doc/api/next_api_changes/2018-10-24-JMK.rst b/doc/api/next_api_changes/2018-10-24-JMK.rst
@@ -0,0 +1,7 @@
+Matplotlib.use now has an ImportError for interactive backend
+-------------------------------------------------------------
+
+Switching backends via `matplotlib.use` is now allowed by default,
+regardless of whether `matplotlib.pyplot` has been imported. If the user
+tries to switch from an already-started interactive backend to a different
+interactive backend, an ImportError will be raised.
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1326,7 +1326,7 @@ def __exit__(self, exc_type, exc_value, exc_tb):
         self.__fallback()
 
 
-def use(arg, warn=True, force=False):
+def use(arg, warn=False, force=True):
     """
     Set the matplotlib backend to one of the known backends.
 
@@ -1352,11 +1352,12 @@ def use(arg, warn=True, force=False):
         If True, warn if this is called after pyplot has been imported
         and a backend is set up.
 
-        defaults to True
+        defaults to False.
 
     force : bool, optional
-        If True, attempt to switch the backend.  This defaults to
-        False.
+        If True, attempt to switch the backend.   An ImportError is raised if
+        an interactive backend is selected, but another interactive
+        backend has already started.  This defaults to True.
 
     See Also
     --------
