preferred syntax for list extend?

[Aahz]

In article <a9kjh1$qc5$1 at slb1.atl.mindspring.net>,
Andrew Dalke <dalke at dalkescientific.com> wrote:
>
>while += is defined as
>
>list_inplace_concat(PyListObject *self, PyObject *other)
>{
> other = PySequence_Fast(other, "argument to += must be iterable");
> if (!other)
>  return NULL;
>
> if (listextend_internal(self, other) < 0)
>  return NULL;
>
> Py_INCREF(self);
> return (PyObject *)self;
>}
>
>The code is almost identical, except for that return self part.
>(I don't know why that's needed.)

Heh.  That's because of the way __iadd__ works.  Immutable objects must
return a new object with __iadd__; mutable objects *MAY* return self
(and usually do).
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

What if there were no rhetorical questions?