I think you are asking about the Exists method: i'm not an expert but i have use in my Tk Tartaglia's triangle fun - Pascal's triangle fun. Here the relevant part (found in subs: destroy_tri draw_triangle): 
if (! Exists($top_lvl_win)) {
    $top_lvl_win= $mw->Toplevel();

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See also zentara's example: Re: How do I determine if a Tk window exists?
The Exists method is in Widget.


HtH
L*
There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

In reply to Re: How can I find out whether a Tk Toplevel widget has been destroyed? by Discipulus
in thread How can I find out whether a Tk Toplevel widget has been destroyed? by tkguifan

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