On 30.09.2019 01:41, Steven D'Aprano wrote: > [...] > But subscripting (indexing) is a conspicuous exception. There's no ABC > for testing whether something supports subscripting.
+1 for adding an ABC to signal support for indexing. BTW: Something I miss in the ABCs is the distinction between indexing using integers for the purpose of accessing a member by position (e.g. in a sequence) and that of indexing objects by way of a key object (let's say a string in e.g. a mapping). Algorithms will typically only work with one type of indexing and the two also use different exceptions to signal "no such member": IndexError for the positional lookups vs. KeyError for the key object lookups. There's no way to map this to special methods, since both mechanisms use .__getitem__(), so the ABC would actually provide information which you can otherwise not easily determine. Perhaps we could have PositionIndexable and KeyIndexable for this (or some other names). Indexable would then be their base class and not allow for the distinction or permit both. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Experts (#1, Oct 01 2019) >>> Python Projects, Coaching and Consulting ... http://www.egenix.com/ >>> Python Database Interfaces ... http://products.egenix.com/ >>> Plone/Zope Database Interfaces ... http://zope.egenix.com/ ________________________________________________________________________ ::: We implement business ideas - efficiently in both time and costs ::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 http://www.egenix.com/company/contact/ http://www.malemburg.com/ _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/JELLH7FVTMZLNXQ2LZSZLRTQMQEM6TDZ/ Code of Conduct: http://python.org/psf/codeofconduct/
