I'm still not seeing why these changes are sufficiently desirable to justify the code churn.  Nor am I seeing test or doc changes that would explain the advantages of the new way, and prevent future regressions.

I agree that the changes would make the signatures better for the typical use cases for this particular widget -- but wouldn't they also break the common interface for the "set" and "activate" methods across several types of tkinter widget?  

If so, then instead of changing or restricting the method, it would be better to add examples (and maybe even an explanation) to the documentation (including the docstring).




In particular:

(1)  Why change actrivate's parameter from "index" to "element"?  I agree that "element" is a better name for the normal case, but 
https://docs.python.org/dev/library/tkinter.html#the-index-parameter
strongly suggests that "index" is more consistent with the rest of tkinter, and that there are use cases wehre "index" is the right name.  If that is not true, please say so explicitly, at least in comments.

(2)  Why change the "set" method?  I understand that a more specific signature is desirable, and I assume that other values would be ignored (or raise an exception), but the set method seems to have an existing API across several widgets -- and that shouldn't be broken lightly.