On Monday 14 November 2016 16:04, Chris Angelico wrote:
> True, but ISTR there being a possibility that __iter__ could raise to
> indicate that this isn't actually iterable. Maybe I'm recalling wrong.
If __iter__ raises, that's a bug :-)
Raising an exception from __iter__ appears to just fall through. There doesn't
seem to be any special handling:
py> class X:
... def __iter__(self):
... raise TypeError("foo")
...
py> iter(X())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in __iter__
TypeError: foo
Contrast that to actual non-iterables:
py> iter(23)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
The way to indicate a class is not iterable is to not give it an __iter__
method in the first place.
If the class inherits __iter__, and you want to over-ride it, you might try
setting the child class __iter__ to None. That trick works for __hash__. It
doesn't work for __iter__ in Python 3.3, but it might work in more recent
versions.
--
Steven
299792.458 km/s — not just a good idea, it’s the law!
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