[Tutor] how to "forget" some checkbuttons on a window

[Chris Roy-Smith]

Hi
Python 3.6
Ubuntu 18.04

I am trying to hide some Checkbuttons.

here is my code:
=====================================
#! /usr/bin/python3
from tkinter import *
testDat=[0,1,2,3,4,5,6,7,8,9]
def    remove(e):
     for i in range(9):
         r=var[i].get()
         if r==True:
             e[i].forget()

master=Tk()
master.title('experiment')

e=[" " for i in range(len(testDat))]
var=[IntVar() for i in range(len(testDat))]
for i in range(len(testDat)):
     e[i]=Checkbutton(master, text=str(i), variable=var[i], 
onvalue=True, offvalue=False).grid(row=i, column=0)
Button(master, text='remove checked', command=lambda i=e: 
remove(i)).grid(row=11, column=0)

master.mainloop()

===================================
I get the following error
===================================

Exception in Tkinter callback
Traceback (most recent call last):
   File "/usr/lib/python3.6/tkinter/__init__.py", line 1705, in __call__
     return self.func(*args)
   File "./frames.py", line 17, in <lambda>
     Button(master, text='remove checked', command=lambda i=e: 
remove(i)).grid(row=11, column=0)
   File "./frames.py", line 8, in remove
     e[i].forget()
AttributeError: 'NoneType' object has no attribute 'forget'

=================================

I was expecting that any checked Checkbuttons to disappear, Obviously 
this doesn't happen, as I get the error on that line.

How do I go about correcting my code?

Regards,
Chris Roy-Smith