On 11/15/06, Josiah Carlson <[EMAIL PROTECTED]> wrote: > > "George Sakkis" <[EMAIL PROTECTED]> 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.
To avoid leading this to a digression about optional typing, my point was that what len() does is a builtin postcondition, and if, for some perverse reason, someone wants to define negative or complex lengths for his perverse class, he'll hit into a wall. Is this yet another case of practicality beating purity hands down ? George _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
