Python empties the contents of idle __python

Python code: clearwindow.py
"""


Clear Window Extension
version:0.2


It provides "clear Shell window" under "Options"
With ability to undo.


Add these lines to Config-extensions.def


[ClearWindow]
Enable=1
Enable_editor=0
Enable_shell=1
[Clearwindow_cfgbindings]
Clear-window=<control-key-l>




"""


Class ClearWindow:


Menudefs = [
(' Options ', [None,
(' Clear Shell Window ', ' <<clear-window>> '),
]),]


def __init__ (self, Editwin):
Self.editwin = Editwin
Self.text = Self.editwin.text
Self.text.bind ("<<clear-window>>", Self.clear_window2)


Self.text.bind ("<<undo>>", self.undo_event) # add= "+" doesn ' t work


def undo_event (self, event):
Text = Self.text


Text.mark_set ("Iomark2", "Iomark")
Text.mark_set ("Insert2", "Insert")
Self.editwin.undo.undo_event (Event)


# fix Iomark and insert
Text.mark_set ("Iomark", "IOMARK2")
Text.mark_set ("Insert", "Insert2")
Text.mark_unset ("Iomark2")
Text.mark_unset ("Insert2")




def clear_window2 (self, event): # Alternative method
# work around the Modifiedundodelegator
Text = Self.text
Text.undo_block_start ()
Text.mark_set ("Iomark2", "Iomark")
Text.mark_set ("Iomark", 1.0)
Text.delete (1.0, "Iomark2 Linestart")
Text.mark_set ("Iomark", "IOMARK2")
Text.mark_unset ("Iomark2")
Text.undo_block_stop ()
If Self.text.compare (' Insert ', ' < ', ' Iomark '):
Self.text.mark_set (' Insert ', ' end-1c ')
Self.editwin.set_line_and_column ()


def clear_window (self, event):
# Remove Undo Delegator
Undo = Self.editwin.undo
Self.editwin.per.removefilter (undo)


# Clear the window, but preserve current command
Self.text.delete (1.0, "Iomark Linestart")
If Self.text.compare (' Insert ', ' < ', ' Iomark '):
Self.text.mark_set (' Insert ', ' end-1c ')
Self.editwin.set_line_and_column ()


# Restore Undo Delegator
Self.editwin.per.insertfilter (undo)


Copy the clearwindow.py file and place it under the Python installation directory, Python xxx\lib\idlelib (XXX is your Python version, for example, 2.7).
Notepad opens the Config-extensions.def (Idle extended configuration file) under the Python xxx\lib\idlelib directory, and to prevent errors, you can copy a backup before opening it.
Modify the Config-extensions.def, add the following at the end, and then save the exit:
[ClearWindow]
Enable=1
Enable_editor=0
Enable_shell=1
[Clearwindow_cfgbindings]
Clear-window=<control-key-;>
Open the Python idle,options option to see the addition of Clear shell window Ctrl +;
Enter the code in the idle and press CTRL +; (refers to Ctrl and;) and find that the code you just entered can be cleared.
Shortcut keys CTRL +; can be modified to a different key to
Clear-window=<control-key-;>
Control and modify the other key.