Tkinter strange behavior on destroy() - python-2.7

Question

I am developing an application on Tkinter, Python 2.7.
In one of my processes I build a portion of my window (root) with 26 widgets:
23 Labels, 2 Buttons and 1 Entry.
While building them I keep adding their names to a list for further destroying
when their use is finished. For that I use the press of one of the buttons ("Done")
to read the list created and destroy() them inside a "for" loop.
The widgets get destroyed erratically, not in the order on the list. And I need
several presses of the button to finish it.
I found out of frustration, not insight, that if the list is reversed() in
the "for" loop they all get "destroyed" in the first attempt.
Is this an expected behaviour? Very puzzling!
I am ready to post the portion of my application with the strange behavior
expunged of unnecessary code unless somebody already knows the reason for it.
I am still busting my chops with Python and not ready to use Classes...
Thank you!
I am including the relevant portion of my program. I edited the original to reduce it size. Tested the edited version and it has the same behavior. I commented some of my code to show where to correct.
Happy that Mr. Oakley has taken interest. I am not sure if on transcribing my code the proper indentation was not affected.
My code:
# testdestroy.py
from Tkinter import *
root = Tk()
root.title('Information container')
root.geometry('1160x900+650+50')
global todestroy, screen, font1, lbl1txt, lbl2txt
global col, row, colincr, rowincr, bxincr, entries
todestroy = []
screen = ''
col = 10
row = 10
font1 = 'verdana 12 bold '
colincr = 370
rowincr = 40
bxincr = 145
entries = {' Last updated: ' : '11/08/2016 at 11:55',
' Login id: ' : 'calfucura',
' Password: ': 'munafuca',
'card number' : '1234567890',
'check number': '445',
'expiry' : '12/06/2018',
'PIN' : '9890',
'Tel:' : '1-800-234-5678',
'emergency' : 'entry nine',
'use for' : 'gas, groceries'}
def position(col, row, what): # returns the position for the place command
colincr = 370
rowincr = 40
bxincr = 145
if what == 'down':
row += rowincr
col -= colincr
if what == 'side':
col += colincr
if what == 'button1':
row += rowincr
col += colincr - bxincr
if what == 'button':
col -= bxincr
if what == 'reset':
col = col
row = row
return col, row
def done(event): # Button "Done"
print 'Done pressed'
for name in todestroy: # DOES NOT WORK!!!!
# THIS WORKS in the previous line:
# for name in reversed(todestroy):
name.destroy()
todestroy.remove(name)
def accept(event): # Button "Accept"
print 'Name to show: ', entry1.get()
scr2d1(entries)
def scr2d(): # Name to show
lbl1txt = 'Enter name to show: '
screen = 'scr2d'
scr2(lbl1txt)
# scr2d1(entries)
def scr2(lbl1txt):
global todestroy, col, row, entry1
lbl1 = Label(root, text = lbl1txt, anchor = E, width = 25, font = font1)
entry1 = Entry(root, width = 25, show = '*', font = font1)
Accept = Button(root, text = 'Accept', font = font1, bg = 'green', width = 9)
cmd = eval('Accept'.lower())
Accept.bind('<ButtonRelease-1>', cmd)
col, row = position(200, 200, 'reset')
lbl1.place(x = col, y = row)
col, row = position(col, row, 'side')
entry1.place(x = col , y = row )
col, row = position(col, row, 'button1')
Accept.place(x = col, y = row)
todestroy = []
todestroy.extend([lbl1, entry1, Accept])
def scr2d1(entries): # show entries
global todestroy, col, row
lblup = 1
lbl = 'lbl' + str(lblup)
lbl = Label(root, text = 'Entry', font = font1, width = 20 )
row = rowincr * 7
col = 600
col, row = position(col, row, 'down')
lbl.place(x = col, y = row)
todestroy.append(lbl)
lblup += 1
lbl = 'lbl' + str(lblup)
lbl = Label(root, text = 'Contents', font = font1, width = 20)
col, row = position(col, row, 'side')
lbl.place (x = col, y = row)
todestroy.append(lbl)
for name in sorted(entries):
lblup += 1
lbl = 'lbl' + str(lblup)
lbl = Label(root, text = name, bg = 'yellow', font = font1, width = 25, anchor = E)
col, row = position(col, row, 'down')
lbl.place(x = col, y = row)
todestroy.append(lbl)
lblup += 1
lbl = 'lbl' + str(lblup)
lbl = Label(root, text = entries[name], bg = 'yellow', font = font1, width = 25, anchor = W)
col, row = position(col, row, 'side')
lbl.place(x = col , y = row)
todestroy.append(lbl)
cmd = eval('done')
Done = Button(root, text = 'Done', font = font1, bg = 'green', width = 9)
Done.bind('<ButtonRelease-1>', cmd)
col, row = position(col, row, 'button1')
Done.place(x = col, y = row)
todestroy.append(Done)
scr2d()
root.mainloop()

Answer 1

The problem is that you are altering the list as you iterate over it, which is not something you should do. The reason that it works with reversed is because you are iterating over a copy of the original list. You get the same result if you use for name in todestroy[:], which also iterates over a copy of the list.
The quickest solution is to not remove anything from the list,and simply reset the list after you've deleted everything:
def done(event):
global todestroy
for name in todestroy:
name.destroy()
todestroy = []
A better solution would be to put all of the widgets you plan to destroy into a Frame. You can then destroy just the frame, and it will destroy all of its child widgets.