[Chicago] duck typing to handle a string or iterable of strings

[Alex Gaynor]

On Thu, May 19, 2011 at 10:34 PM, Carl Meyer <carl at oddbird.net> wrote:

> On 05/19/2011 10:13 PM, Jesse London wrote:
> > It sounds like what you really care about is whether or not you were
> > handed an iterable. If you don't want to say:
> >
> >     def foo(*strings):
> >         ...
> >
> > then you can reliably duck-type like so:
> >
> >     def foo(strings):
> >         if not hasattr(strings, '__iter__'):
> >             strings = (strings,)
> >         ...
>
> Not in Python 3, FWIW. Since strings are an iterable, it was really only
> ever an oversight that they lacked __iter__, and that was fixed in Python
> 3.
>
> Carl
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>

It wasn't in any way an oversight, in fact the __iter__ on list and tuples
are totally superflous.  Types which define __getitem__ are automatically
iterable and a default iterator is used for them which calls __getitem__
with successive integers until an IndexError is raised.

Alex

-- 
"I disapprove of what you say, but I will defend to the death your right to
say it." -- Evelyn Beatrice Hall (summarizing Voltaire)
"The people's good is the highest law." -- Cicero
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