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[Python-Dev] PySequence_Check but no __len__

Terry Reedy tjreedy at udel.edu
Fri Jun 22 15:07:32 EDT 2018 
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__.

-- 
Terry Jan Reedy
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