status of Programming by Contract (PEP 316)?

[Russ]

> PEP 316 introduces new syntax for a limited use feature. That's pretty
> much a no-starter, in my opinion, and past experience tends to bear
> that out. Furthermore, it predates decorators  and context managers,
> which give all the syntax support you need and let you move the actual
> DBC features into a library. I can't remember if I mentioned this
> before but I believe that Philip Ebys PEAK toolkit has some stuff you
> could use for DBC.

I don't see how you can avoid adding some new syntax, given that
Python does not
currently have syntax for specifying invariants and pre- and post-
conditions. And if I am
not mistaken, the new syntax would appear only in doc strings, not in
the regular Python
code itself. We're not really talking here about changing the core
Python syntax itself,
so I don't see it as a "non-starter." Anyone who chooses not to use
would be completely
unaffected.

As far as I can tell, Terence Way has done a nice job of implementing
design by contract for
Python, but perhaps a better approach is possible. The advantage of
making part of the
core Python distribution is that it would get vetted more thoroughly.