New to Python: Features

[Cameron Laird]

In article <1gl97ps.endfhf1dfa6l0N%aleaxit at yahoo.com>,
Alex Martelli <aleaxit at yahoo.com> wrote:
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>Bully for you -- I don't.  I wish I could set a callback on a given
>object getting modified or a given name getting rebound - but I can't,
>not with enough generality and little-enough black magic to be usable in
>production code.
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Tcl provides an interesting comparison.  Tcl builds in what
it calls [trace]s <URL: http://wiki.tcl.tk/trace >--and there-
fore, of course, so does (Tkinter-importing) Python!

I summarize Tcl's experience from a personal perspective:
* degradation of performance has been less than
  anyone has a right to expect, mostly due to a
  lot of good engineering by several contributors;
* traces definitely are useful, and contribute to
  Tcl's character;
* they're an intermediate-to-advanced construct.
  They warp coders' notion of source-code locality,
  and frustrate some programmers' debugging efforts
  a great deal.  Others never seem to have problems
  with them.  I use traces rarely, am glad they're
  available when I do, and they give me essentially
  no headaches.

I suspect the callback I understand you're describing would
alarm at least some of Pythonia--the language wouldn't feel
as safe, particularly for collaboration, as it does now.