Decorator for Enforcing Argument Types

[Peter Wang]

Bruno Desthuilliers wrote:
> <my humble opinion>
> Python is dynamic, and fighting against the language is IMHO a really
> bad idea. The only places where theres a real need for this kind of
> stuff are when dealing with the "outside world" (IOW : inputs and
> outputs). And then packages like formencode can do much more than mere
> type-checking
> </my humble opinion>

I don't think proper use of type checking is "fighting against the
language".  The goal of any language is to enable programmers to
express their intent in a form that executes correctly.

Python is extremely expressive but there is a trade-off with
correctness - you can easily say something that you don't mean.  Unit
testing is sometimes sufficient, but it can never span the infinite
space of potential errors.  Type-checking method signatures guarantees
a certain amount of low-level correctness, and most type-checking
mechanisms also serve as documentation aids.

I think that with a sufficiently sophisticated type checking syntax,
one can get the best of both worlds.  If the type checker understood
interfaces (like PyProtocols) and its syntax had the flexibility to
indicate sets of allowed arguments and aggregates of allowed
types/interfaces, it would cover the majority of cases without limiting
expressive power.

I understand that we're all adults, but it's still nice to have the
computer tell us when we're being childish. :)


-peter