Hello,

I am building a program with Tkinter. However, I found the Optionmenu widget has inconsistent behaviors on default lengths on a Mac and a Windows PC. 

So I set the width of an optionmenu through menu.configure(width=70). On Windows, this correctly sets the menu width to 70 when the program runs. However, on a Mac, the menu is still very narrow at the start. It only expands to 70 after I select an option. 

I have attached a screenshot to help explain the issue. It does not occur on Windows.

I suspect this is just a MacOS behaviour, if not then it is a Tk bug. If you really need to enforce the width, you could tell it to expand horizontally in the layout. An example of this would be as follows:

tk.Frame(root, height=1, width=300).pack()
tk.OptionMenu(root, tk.StringVar(), "test").pack(fill="x")

A bit more detail on the Tk side of things:
tkinter doesn't actually use `tk_optionMenu` and instead creates its own menubutton and menu. The issue with the menubutton width not changing also exists when working directly with Tk (`pack [menubutton .p -width 100]`). However, the same behaviour can be shown when using `tk_optionMenu`, so changing tkinter to use that instead would not fix this issue.

This should likely be closed as 3rd party

 zjdavid Which python release, which macOS, which installer, which tk patchlevel?  (IDLE Help=>About displays it).

At least one of the 3.9.1 python.org mac installers installs 8.6.10.  We cannot be responsible for problems fixed in this release.

I concur with E. Paine that you should use pack(fill="x") if you want to stretch a widget. And in any case Tkinter itself does not manage layout, it is just a wrapper around Tk, so if you think that the default layout of a button is wrong on some platforms, you should report it to the Tk team.

Thanks for your help! I agree that it is probably a Tk issue. I will contact them and back with more information.