[Python-Dev] Re: Sets: elt in dict, lst.include - really begs for a PEP

[Eric S. Raymond]

Greg Ewing <greg@cosc.canterbury.ac.nz>:
> Yuck. I don't like any of this "for x in y.iterator_something()"
> stuff. The things you're after aren't "in" the iterator, they're
> "in" the dict. I don't want to know that there are iterators
> involved.

I must say I agree.  Having explicit iterators obfuscates what is
going on, rather than clarifying it -- the details of how we get
the next item should be hidden as far below the surface of the
code as possible, so programmers don't have to think about them.

The only cases I know of where an explicit iterator object is even
semi-justified are those where there is substantial control state to
be kept around between iterations and that state has to be visible to
the application code (not the case with dictionaries or any other
built-in type).  

In the cases where that *is* true (interruptible tree traversal being
the paradigm example), we would be better served with Icon-style
generators or a continuations facility a la Stackless Python.

I'm a hard -1 on explicit iterator objects for built-in types.  Let's
keep it simple, guys.
-- 
		<a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a>

The Constitution is not neutral. It was designed to take the
government off the backs of the people.
	-- Justice William O. Douglas