Capture errors in user's input lines and raises meaningfull exceptions.

IPython/frontend/linefrontendbase.py

@@ -21,6 +21,7 b' import re'
 import IPython
 import sys
 import codeop
+import traceback
 
 from frontendbase import FrontEndBase
 from IPython.kernel.core.interpreter import Interpreter
@@ -147,10 +148,18 b' class LineFrontEndBase(FrontEndBase):'
                         and not re.findall(r"\n[\t ]*\n[\t ]*$", string)):
             return False
         else:
+            self.capture_output()
+            try:
             # Add line returns here, to make sure that the statement is
             # complete.
-            return codeop.compile_command(string.rstrip() + '\n\n',
+                is_complete = codeop.compile_command(string.rstrip() + '\n\n',
                         "<string>", "exec")
+                self.release_output()
+            except Exception, e:
+                # XXX: Hack: return True so that the
+                # code gets executed and the error captured.
+                is_complete = True
+            return is_complete
 
 
     def write(self, string, refresh=True):

IPython/frontend/wx/wx_frontend.py

@@ -324,6 +324,17 b' class WxController(ConsoleWidget, PrefilterFrontEnd):'
 
     
     #--------------------------------------------------------------------------
+    # FrontEndBase interface 
+    #--------------------------------------------------------------------------
+    
+    def render_error(self, e):
+        start_line = self.GetCurrentLine()
+        self.write('\n' + e + '\n')
+        for i in range(start_line, self.GetCurrentLine()):
+            self._markers[i] = self.MarkerAdd(i, _ERROR_MARKER)
+
+
+    #--------------------------------------------------------------------------
     # ConsoleWidget interface 
     #--------------------------------------------------------------------------