tkinter cascaded menus, was Re: PyTk cascaded radiobuttons, howto?

[Peter Otten]

nickgeovanis at gmail.com wrote:

> Using python 3.4.2.
> Tcl/tk example here is from /usr/share/tk8.5/demos/widget and
> .../menu.tcl. The way tcl/tk adds cascaded radiobuttons to a menu is like
> this: set m $w.menu.cascade
> $w.menu add cascade -label "Cascades" -menu $m -underline 0
> ....
> $m add cascade -label "Radio buttons" -menu $w.menu.cascade.radio...
> set m $w.menu.cascade.radio
> $m add radio -label "Roman" -variable style...
> $m add radio -label "Italic" -variable style...
> 
> ...and so on.
> 
> My difficulty doing the same in PyTk is the following: When creating that
> uppermost cascade, you do something like menu.add_cascade(label =
> "Cascades") ...but there is no ability to save a usable reference to that
> top-level cascade. If I do so anyway and add a radiobutton to it, nothing
> appears, no errors either. What is the correct way to cascade radiobuttons
> from a cascaded menu in PyTk? Thanks....Nick

You build the inner menu and then add it to the outer.

After looking into the examples in the Demo/tkinter folder of the Python 2.7 
source distribution I came up with the following:

import tkinter
from tkinter import Menu

root = tkinter.Tk()

menubar = Menu(root)

editmenu = Menu(menubar)

editmenu.add_command(label="Cut")
editmenu.add_command(label="Copy")
editmenu.add_command(label="Paste")

fontmenu = Menu(editmenu, name="font")
fontmenu.add_command(label="Family")
fontmenu.add_command(label="Size")
editmenu.add_cascade(label="Font", menu=fontmenu)

colormenu = Menu(editmenu, name="color")
colormenu.add_radiobutton(label="Red")
colormenu.add_radiobutton(label="Yellow")
colormenu.add_radiobutton(label="Blue")
fontmenu.add_cascade(label="Color", menu=colormenu)

menubar.add_cascade(label="Edit", menu=editmenu)

root["menu"] = menubar
root.mainloop()