On 22.06.2018 22:07, Terry Reedy wrote:
On 6/22/2018 7:17 AM, Christian Tismer wrote:
My problem is to find out how to deal with a class which has
__getitem__ but no __len__.
The documentation suggests that the length of a sequence can always
be obtained by len().
https://docs.python.org/3/reference/datamodel.html
It says that plainly: "The built-in function len() returns the number
of items of a sequence. "
https://docs.python.org/3/library/collections.abc.html#collections-abstract-base-classes
says that a Sequence has both __getitem__ and __len__.
I am surprised that a C-API function calls something a 'sequence'
without it having __len__.
A practical sequence check is checking for __iter__ . An iterator
doesn't necessarily have a defined length -- e.g. a stream or a generator.
--
Regards,
Ivan
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
