[Zope3-dev] Re: [Zope3-checkins] SVN: Zope3/trunk/src/zope/schema/interfaces.py - add IIterableChoice and note the desire to depricate vocabularies

[Stuart Bishop]

Benji York wrote:

> +class IIterableSource(Interface):
> +    """Source which supports iteration over allowed values.
> +
> +    The objects iteration provides must be values from the source.
> +    """
> +
> +    def __iter__():
> +        """Return an iterator which provides the values from the source."""
> +
> +    def __len__():
> +        """Return the number of valid values, or sys.maxint."""

If a Source is iterable, it should never have an (effectively) infinite
length, should it?

If this is a way of saying "I'm iterable, but I don't want to tell you how
long I am" (such as iterating over the results from a database query where
you would have to suck them into RAM or issue the query twice to know),
shouldn't an exeption be raised? Otherwise 'for i in range(0,len(source)):
foo = source[i]' could start blowing up if the source changes.

-- 
Stuart Bishop <stuart at stuartbishop.net>
http://www.stuartbishop.net/
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