On Wed, Sep 21, 2011 at 11:41:58AM -0700, Reid Price wrote:
> On Wed, Sep 21, 2011 at 10:58 AM, Ben Pfaff <[email protected]> wrote:
>
> > I wish there was a simple way to just test for "iterable" and
> > "mapping" types (is there?). Then we could get rid of a lot of ugly
> > tests for specific types, in favor of more general tests.
> >
>
> The standard way to determine iterables is with
>
> hasattr(obj, '__iter__')
>
> It's not the prettiest (and note behavior with strings/unicode), but it
> generally behaves as expected.
> There isn't a great way to determine whether something is a 'map' in
> general, as {}[key] and [][index]
> both use the __getitem__ method. In practice, it is fairly rare to see
> non-dict maps.
The Python reference manual says:
It is also recommended that mappings provide the methods
keys(), values(), items(), has_key(), get(), clear(),
setdefault(), iterkeys(), itervalues(), iteritems(), pop(),
popitem(), copy(), and update() behaving similar to those for
Python's standard dictionary objects.
That seems to distinguish in practice:
>>> hasattr({}, "iterkeys")
True
>>> hasattr([], "iterkeys")
False
Any comment on whether how (un)wise it might be to use this to
distinguish maps from simple sequences?
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