Clarify allowable backend switches in matplotlib.use().

anntzer · anntzer · commit 53b5ed97b1ca · 2021-07-04T23:37:09.000+02:00
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1074,11 +1074,16 @@ def use(backend, *, force=True):
 
         or a string of the form: ``module://my.module.name``.
 
+        Switching to an interactive backend is not possible if an unrelated
+        event loop has already been started (e.g., switching to GTK3Agg if a
+        TkAgg window has already been opened).  Switching to a non-interactive
+        backend is always possible.
+
     force : bool, default: True
         If True (the default), raise an `ImportError` if the backend cannot be
         set up (either because it fails to import, or because an incompatible
-        GUI interactive framework is already running); if False, ignore the
-        failure.
+        GUI interactive framework is already running); if False, silently
+        ignore the failure.
 
     See Also
     --------
