--- Revision None
+++ Revision 343037313465
@@ -0,0 +1,20 @@
+# http://www.norvig.com/python-iaq.html
+h = [None]  # history
+
+class Prompt:
+    """
+    A prompt a history mechanism.
+    From http://www.norvig.com/python-iaq.html
+    """
+    def __init__(self, prompt='h[%d] >>> '):
+        self.prompt = prompt
+
+    def __str__(self):
+        try:
+            if _ not in h: h.append(_)
+        except NameError:
+            pass
+        return self.prompt % len(h)
+
+    def __radd__(self, other):
+        return str(other) + str(self)