Thank you for your explanation! ᐧ On Thu, Jan 18, 2018 at 11:00 PM, Guido van Rossum <gu...@python.org> wrote:
> On Thu, Jan 18, 2018 at 7:51 PM, Nikolas Vanderhoof < > nikolasrvanderh...@gmail.com> wrote: > >> I sometimes wish that Python included a richer set of assertions rather >>> than just a single `assert` keyword. Something like Eiffel's concept of >>> pre-conditions, post-conditions and invariants, where each can be >>> enabled or disabled independently. >> >> >> Has something like this been proposed for Python before? >> This seems to align more with the intended use of assert that's been >> pointed out in this thread. >> In what case though would one want to disable some but not all of these >> pre, post, or invariant assertions? >> > > Oh, many times, starting in the late '90s IIRC (Paul Dubois was a big fan). > > The problems are twofold: (a) it would require a lot of new keywords or > ugly syntax; and (b) there would have to be a way to enable each form > separately *per module or package*. Eiffel solves that (AFAIC) through > separate compilation -- e.g. a stable version of a library might disable > invariants and post-conditions but keep pre-conditions, since those could > be violated by less mature application code; or a mature application could > disable all checks and link with optimized library binaries that also have > disabled all checks. I'm sure other scenarios are also viable. > > But that solution isn't available in Python, where command line flags > apply to *all* modules being imported. > > (Note: even if you have a solution for (b), getting past (a) isn't so > easy. So don't get nerd-sniped by the solution for (b) alone.) > > -- > --Guido van Rossum (python.org/~guido) >
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