entry widget won't validate

[Mike]

On Sep 21, 12:47 pm, Peter Otten <__pete... at web.de> wrote:
> Mike wrote:
> > I'm trying to arrange for an Entry widget to check whether its data
> > is all digits and whether the number represented is small enough.
> > The validate function seem to be called once at startup and not
> > afterwards:


> > The print statement run 3 times at startup.
> > Editing an Entry does not cause any printing.
> > Any ideas?
>
> Quotinghttp://www.tcl.tk/man/tcl8.5/TkCmd/entry.htm#M12:
>
> """
> In general, the textVariable and validateCommand can be dangerous to mix.
> Any problems have been overcome so that using the validateCommand will not
> interfere with the traditional behavior of the entry widget. Using the
> textVariable for read-only purposes will never cause problems. The danger
> comes when you try set the textVariable to something that the
> validateCommand would not accept, which causes validate to become none (the
> invalidCommand will not be triggered). The same happens when an error occurs
> evaluating the validateCommand.
> """
>
> You can verify that this is indeed your problem by changing the Levels.vc()
> method to always return True for the moment.

Returning True does seems to cause vc to be called more often.
I'm still not getting the data I want though.
The variable always gives me the pre-change string.
I gather I need to do something with "%P".
google gave me hints that I should use something called "register",
but I'm not at all clear on what I should do with them.
I don't know how to translate from Tcl to python.