plt.show warns if a non-GUI backend is being used

zhoubecky · zhoubecky · commit a676944a57cb · 2018-03-05T11:50:35.000-05:00
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -175,20 +175,28 @@ def draw_if_interactive(cls):
                 cls.trigger_manager_draw(manager)
 
     @classmethod
-    def show(cls, block=None):
+    def show(cls, block=None, warn=True):
         """Show all figures.
 
         `show` blocks by calling `mainloop` if *block* is ``True``, or if it
         is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
         `interactive` mode.
         """
-        if cls.mainloop is None:
-            return
         managers = Gcf.get_all_fig_managers()
         if not managers:
             return
         for manager in managers:
-            manager.show()
+            try:
+                manager.show()
+            except NonGuiException:
+                if warn:
+                    import warnings
+                    warnings.warn(
+                        "matplotlib is currently using a non-GUI backend, "
+                        "so cannot show the figure")
+                return
+        if cls.mainloop is None:
+            return        
         if block is None:
             # Hack: Are we in IPython's pylab mode?
             from matplotlib import pyplot
