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x is sequence-like if it provides __getitem__() but not keys()
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So why does this barf?
>>> [].__getitem__ Traceback (most recent call last): File "<stdin>", line 1, in ? AttributeError: __getitem__
(Obviously, lists *do* understand __getitem__ at some level. Why isn't it exposed in the method table?)
The old type/class split: list is a type, and types spell their "method tables" in ways that have little in common with how classes do it. See PyObject_GetItem in abstract.c for gory details (e.g., dicts spell their version of getitem via ->tp_as_mapping->mp_subscript(...), while lists spell it ->tp_as_sequence->sq_item(...); neither has any binding to the attr "__getitem__"; instance objects fill in both the tp_as_mapping and tp_as_sequence slots, then map both the mp_subscript and sq_item slots to classobject.c's instance_item, which in turn looks up "__getitem__"). bet-you're-sorry-you-asked<wink>-ly y'rs - tim