[Python-3000] Builtin iterator type

[Josiah Carlson]

"George Sakkis" <gsakkis at rutgers.edu> wrote:
> You missed my point; I wasn't seriously suggesting that there should
> be more checks (hence the quotes), but rather the contrary, that
> checking whether len() returns a non-negative integer does very little
> to the overall consistency scheme of things.
> 
> Pre-conditions, post-conditions, invariants are a stricter form of API
> conformance than just checking whether a method with a specific name
> is there, and Python is unwilling to check even that.

No, it's not that Python is unwilling, we just haven't found the need. 
For people who want/need to _enforce_ preconditions, postconditions,
invariants, etc., Python 2.4 introduced a decorator syntax that makes it
(arguably) trivial to declare such things...

@typecheck((int, long), (int, long), (int, long, float))
@precondition(ARG > 0, 0 < ARG < 10, NOTIN(inf, NaN, -inf))
@postcondition(NOTIN(inf, NaN, -inf))
def fcn(a, b, c):
    ...

Given proper definitions of typecheck, precondition, postcondition, ARG
and NOTIN.

For the rest of us who document, use unit testing (with or without the
unittest framework), etc., thinking of development in terms of what we
learned in school for developing C, C++, or Java seems backwards (at
least in my opinion).  I can spend days writing all of that crap, or I
can spend a few hours writing the software with unittests in Python.

 - Josiah