There are two different kinds of TypeError: if the end user passes an instance of wrong type and if the author of the library makes an error in implementation of some protocols.
For example, len(obj) raises TypeError in two cases: if obj does not have __len__ (user error) and if obj.returns non-integer (implementation error). for x in obj raises TypeError if obj does not have __iter__ (user error) and if iter(obj) does not have __next__ (implementation error). User errors can be fixed on user side, implementation errors can only be fixed by the author of the class. Even if the user and the author is the same person, these errors point to different places of code. Would it be worth to add a special TypeError subclass for implementation errors to distinguish them from user errors? How to name it (ImplementationError, ProtocolError, etc)? _______________________________________________ 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/Y5BBLXXPORROUNWPACTAEIPJZFSKRVHY/ Code of Conduct: http://python.org/psf/codeofconduct/
