Type checking

[Christopher T King]

George Sakkis wrote:

> I wonder if people have come up with such pitfalls in practice or I was just
> careless. In any case, I was tempted enough to write a simple extensible
> runtime type checking module, which can be handy, at least during
> development. It's extensible in the sense that a "type" can be any

And in other places: some functions need to behave differently depending 
on the types of their arguments. When interfaces come into play, 
isinstance() just doesn't cut it.

> ContainerOf, TupleOf, ListOf and DictOf are all extensions of the abstract
> TypeChecker class, providing some limited but common templated-type
> checking. Of course in practice most complex structures (e.g. phonebook)
> would be encapsulated in a class, so it's questionable whether such
> functionality adds up anything to a list of "assert isinstance(object,type)"
> statements. Any ideas or suggestions are welcome.

Along with TupleOf, ListOf, DictOf, etc., include interface checkers, 
such as SequenceOf and MappingOf. People will love you for it.