diff --git a/lib/matplotlib/backends/backend_qt.py b/lib/matplotlib/backends/backend_qt.py
index eb08c734af20..fc6639914d35 100644
--- a/lib/matplotlib/backends/backend_qt.py
+++ b/lib/matplotlib/backends/backend_qt.py
@@ -898,7 +898,7 @@ def _tight_layout(self):
         self._figure.tight_layout()
         for attr, spinbox in self._spinboxes.items():
             spinbox.blockSignals(True)
-            spinbox.setValue(vars(self._figure.subplotpars)[attr])
+            spinbox.setValue(getattr(self._figure.subplotpars, attr))
             spinbox.blockSignals(False)
         self._figure.canvas.draw_idle()
 
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index 04b9bdb79ab2..eef477e34aaa 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -325,11 +325,12 @@ def draw_if_interactive():
     # show is already present, as the latter may be here for backcompat.
     manager_class = getattr(getattr(backend_mod, "FigureCanvas", None),
                             "manager_class", None)
-    # We can't compare directly manager_class.pyplot_show and FMB.pyplot_show
-    # because pyplot_show is a classmethod so the above constructs are bound
-    # classmethods, & thus always different (being bound to different classes).
-    manager_pyplot_show = vars(manager_class).get("pyplot_show")
-    base_pyplot_show = vars(FigureManagerBase).get("pyplot_show")
+    # We can't compare directly manager_class.pyplot_show and FMB.pyplot_show because
+    # pyplot_show is a classmethod so the above constructs are bound classmethods, and
+    # thus always different (being bound to different classes).  We also have to use
+    # getattr_static instead of vars as manager_class could have no __dict__.
+    manager_pyplot_show = inspect.getattr_static(manager_class, "pyplot_show", None)
+    base_pyplot_show = inspect.getattr_static(FigureManagerBase, "pyplot_show", None)
     if (show is None
             or (manager_pyplot_show is not None
                 and manager_pyplot_show != base_pyplot_show)):