diff -r 7e245e785b91 Lib/idlelib/Percolator.py
--- a/Lib/idlelib/Percolator.py	Wed Mar 14 22:42:49 2012 +0100
+++ b/Lib/idlelib/Percolator.py	Wed Mar 14 17:34:16 2012 -0500
@@ -22,7 +22,13 @@
 
     def insert(self, index, chars, tags=None):
         # Could go away if inheriting from Delegator
-        self.top.insert(index, chars, tags)
+        try:
+            self.top.insert(index, chars, tags)
+        except ValueError:  # Issue12342 
+            encoding = 'ascii'
+            s_bytes = chars.encode(encoding, 'backslashreplace')
+            s = s_bytes.decode(encoding, 'strict')
+            self.top.insert(index, s, tags)
 
     def delete(self, index1, index2=None):
         # Could go away if inheriting from Delegator
diff -r 7e245e785b91 Lib/idlelib/PyShell.py
--- a/Lib/idlelib/PyShell.py	Wed Mar 14 22:42:49 2012 +0100
+++ b/Lib/idlelib/PyShell.py	Wed Mar 14 17:34:16 2012 -0500
@@ -1221,16 +1221,6 @@
         self.set_line_and_column()
 
     def write(self, s, tags=()):
-        if isinstance(s, str) and len(s) and max(s) > '\uffff':
-            # Tk doesn't support outputting non-BMP characters
-            # Let's assume what printed string is not very long,
-            # find first non-BMP character and construct informative
-            # UnicodeEncodeError exception.
-            for start, char in enumerate(s):
-                if char > '\uffff':
-                    break
-            raise UnicodeEncodeError("UCS-2", char, start, start+1,
-                                     'Non-BMP character not supported in Tk')
         try:
             self.text.mark_gravity("iomark", "right")
             OutputWindow.write(self, s, tags, "iomark")
diff -r 7e245e785b91 Lib/idlelib/run.py
--- a/Lib/idlelib/run.py	Wed Mar 14 22:42:49 2012 +0100
+++ b/Lib/idlelib/run.py	Wed Mar 14 17:34:16 2012 -0500
@@ -261,26 +261,6 @@
             quitting = True
             thread.interrupt_main()
 
-
-def displayhook(value):
-    """Override standard display hook to use non-locale encoding"""
-    if value is None:
-        return
-    # Set '_' to None to avoid recursion
-    builtins._ = None
-    text = repr(value)
-    try:
-        sys.stdout.write(text)
-    except UnicodeEncodeError:
-        # let's use ascii while utf8-bmp codec doesn't present
-        encoding = 'ascii'
-        bytes = text.encode(encoding, 'backslashreplace')
-        text = bytes.decode(encoding, 'strict')
-        sys.stdout.write(text)
-    sys.stdout.write("\n")
-    builtins._ = value
-
-
 class MyHandler(rpc.RPCHandler):
 
     def handle(self):
@@ -290,7 +270,6 @@
         sys.stdin = self.console = self.get_remote_proxy("stdin")
         sys.stdout = self.get_remote_proxy("stdout")
         sys.stderr = self.get_remote_proxy("stderr")
-        sys.displayhook = displayhook
         # page help() text to shell.
         import pydoc # import must be done here to capture i/o binding
         pydoc.pager = pydoc.plainpager