On 1 Sep 2005 00:52:54 -0700, "talin at acm dot org" <[EMAIL PROTECTED]> wrote:
>Although I realize the perils of even suggesting polluting the Python >namespace with a new keyword, I often think that it would be useful to >consider defining an operator for testing whether or not an item is a >member of a category. > >Currently, we have the 'in' operator, which tests for membership within >a container, and that works very well -- in particular, it allows such >membership tests to be expressed in very natural way. So for example, >whereas in C++ I always have to say: > > if (dependencies.find( name ) != dependencies.end()) > >in Python I can simply say: > > if name in dependencies: > >...which is much more readable and intuitive. At the same time, >however, I recognize that there is a logical difference between >membership in a container, and membership in a category. For example, >although a bear is a member of the class of mammals, it doesn't make as >much to say "if bear in mammal". Similarly, you wouldn't want to use >the 'in' keyword as a replacement for isinstance(), i.e. "if name in >str". > >I propose the word 'isa' because the term 'isa hierarchy' is commonly >used to indicate a tree of types. So the syntax would look like this: > > if bear isa mammal: > if name isa str: > What's the difference between this and ``isinstance`` ? Best Regards, Fuzzy http://www.voidspace.org.uk/python -- http://mail.python.org/mailman/listinfo/python-list
