Make MatplotlibViewer.plot() animate in jupyter notebooks

Fixes usnistgov#584

fipy/viewers/matplotlibViewer/matplotlibViewer.py

@@ -40,6 +40,24 @@
 
 from fipy.viewers.viewer import AbstractViewer
 
+def _isnotebook():
+    """return True if running in a jupyter notebook
+
+    https://stackoverflow.com/a/39662359/2019542
+    """
+    try:
+        import IPython
+
+        shell = IPython.get_ipython().__class__.__name__
+        if shell == 'ZMQInteractiveShell':
+            return True   # Jupyter notebook or qtconsole
+        elif shell == 'TerminalInteractiveShell':
+            return False  # Terminal running IPython
+        else:
+            return False  # Other type (?)
+    except (ImportError, NameError):
+        return False      # Probably standard Python interpreter
+
 class AbstractMatplotlibViewer(AbstractViewer):
     """
     .. attention:: This class is abstract. Always create one of its subclasses.
@@ -158,6 +176,14 @@ def plot(self, filename = None):
         if filename is not None:
             pylab.savefig(filename)
 
+        if _isnotebook():
+            # plots don't animate in the notebook unless we
+            # explicitly clear_output and display
+            from IPython.display import display, clear_output
+
+            clear_output(wait=True)
+            display(self)
+
     def _validFileExtensions(self):
         import pylab
         return ["""