First draft of history msg.

* Added get_history method of InteractiveShell.
* Added history_request/reply msg in ipkernel. I have changed the
  msg format slightly and changed the docs to reflect that.

IPython/core/interactiveshell.py

@@ -1081,6 +1081,54 b' class InteractiveShell(Configurable, Magic):'
                 readline.read_history_file(self.histfile)
         return wrapper
 
+    def get_history(self, index=None, raw=False, output=True):
+        """Get the history list.
+
+        Get the input and output history.
+
+        Parameters
+        ----------
+        index : n or (n1, n2) or None
+            If n, then the last entries. If a tuple, then all in
+            range(n1, n2). If None, then all entries. Raises IndexError if
+            the format of index is incorrect.
+        raw : bool
+            If True, return the raw input.
+        output : bool
+            If True, then return the output as well.
+
+        Returns
+        -------
+        If output is True, then return a dict of tuples, keyed by the prompt
+        numbers and with values of (input, output). If output is False, then
+        a dict, keyed by the prompt number with the values of input. Raises
+        IndexError if no history is found.
+        """
+        if raw:
+            input_hist = self.input_hist_raw
+        else:
+            input_hist = self.input_hist
+        if output:
+            output_hist = self.user_ns['Out']
+        n = len(input_hist)
+        if index is None:
+            start=0; stop=n
+        elif isinstance(index, int):
+            start=n-index; stop=n
+        elif isinstance(index, tuple) and len(index) == 2:
+            start=index[0]; stop=index[1]
+        else:
+            raise IndexError('Not a valid index for the input history: %r' % index)
+        hist = {}
+        for i in range(start, stop):
+            if output:
+                hist[i] = (input_hist[i], output_hist.get(i))
+            else:
+                hist[i] = input_hist[i]
+        if len(hist)==0:
+            raise IndexError('No history for range of indices: %r' % index)
+        return hist
+
     #-------------------------------------------------------------------------
     # Things related to exception handling and tracebacks (not debugging)
     #-------------------------------------------------------------------------

IPython/zmq/ipkernel.py

@@ -55,7 +55,8 b' class Kernel(Configurable):'
 
         # Build dict of handlers for message types
         msg_types = [ 'execute_request', 'complete_request', 
-                      'object_info_request', 'prompt_request' ]
+                      'object_info_request', 'prompt_request',
+                      'history_request' ]
         self.handlers = {}
         for msg_type in msg_types:
             self.handlers[msg_type] = getattr(self, msg_type)
@@ -214,6 +215,16 b' class Kernel(Configurable):'
                                 content, parent, ident)
         print >> sys.__stdout__, msg
 
+    def history_request(self, ident, parent):
+        output = parent['content'].get('output', True)
+        index = parent['content'].get('index')
+        raw = parent['content'].get('raw', False)
+        hist = self.shell.get_history(index=index, raw=raw, output=output)
+        content = {'history' : hist}
+        msg = self.session.send(self.reply_socket, 'history_reply',
+                                content, parent, ident)
+        print >> sys.__stdout__, msg
+
     def start(self):
         while True:
             ident = self.reply_socket.recv()

docs/source/development/messaging.txt

@@ -372,15 +372,18 b' Message type: ``history_request``::'
 
     content = {
     
-      # If true, also return output history in the resulting dict.
+      # If True, also return output history in the resulting dict.
       'output' : bool,
 
-      # This parameter can be one of: A number,  a pair of numbers, 'all'
+      # If True, return the raw input history, else the transformed input.
+      'raw' : bool,
+
+      # This parameter can be one of: A number,  a pair of numbers, None
       # If not given, last 40 are returned.
       #  - number n: return the last n entries.
       #  - pair n1, n2: return entries in the range(n1, n2).
-      #  - 'all': return all history
-      'range' : n or (n1, n2) or 'all',
+      #  - None: return all history
+      'range' : n or (n1, n2) or None,
 
       # If a filter is given, it is  treated as a regular expression and only
       #  matching entries are returned.  re.search() is used to find matches.
@@ -390,14 +393,11 b' Message type: ``history_request``::'
 Message type: ``history_reply``::
 
     content = {
-      # A list of (number, input) pairs
-      'input' : list,
-      
-      # A list of (number, output) pairs
-      'output' : list,
-      }
-
-    
+      # A dict with prompt numbers as keys and either (input, output) or input
+      # as the value depending on whether output was True or False,
+      # respectively.
+      'history' : dict,
+    }
 Messages on the PUB/SUB socket
 ==============================