But the text of the error message will explain all you need for debugging and testing.
On Fri, Sep 3, 2021 at 10:08 AM Christopher Barker <python...@gmail.com> wrote: > > > On Fri, Sep 3, 2021 at 9:35 AM Guido van Rossum <gu...@python.org> wrote: > >> The question is, would anyone ever want to make a distinction between the >> two in *real* code? >> > > I expect not. > > However, finer grained exception may help with debugging and testing. > > -CHB > > > > > find it unlikely that someone would write >> >> try: >> sum(x, y, z) >> except TypeError: >> ... >> >> If you bury the sum() call deep inside other code, I'd say your >> try/except net is too wide. >> >> On Fri, Sep 3, 2021 at 4:24 AM Oscar Benjamin <oscar.j.benja...@gmail.com> >> wrote: >> >>> On Fri, 3 Sept 2021 at 08:10, Serhiy Storchaka <storch...@gmail.com> >>> wrote: >>> > >>> > 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)? >>> >>> I think that it would be good to make TypeError more fine-grained. >>> Another example is: >>> >>> >>> sum(1, 2, 3) >>> Traceback (most recent call last): >>> File "<stdin>", line 1, in <module> >>> TypeError: sum() takes at most 2 arguments (3 given) >>> >>> There can be reasons in library code to catch TypeError that might >>> arise from bad user input but in those situations you would usually >>> not want to catch this TypeError. The error from calling a function >>> with the wrong number of arguments would usually mean a bug in the >>> library code which should not be caught. Conversely if the user input >>> is a callable and you do want to catch the error resulting from it >>> being called with the wrong number of arguments then catching >>> TypeError is too broad again. Something like BadArgumentsError would >>> be better. >> >> >>> >>> -- >>> Oscar >>> _______________________________________________ >>> 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/3CLXFC52JIBCFXMXRFA5I6F4RDU5ZYP3/ >>> Code of Conduct: http://python.org/psf/codeofconduct/ >>> >> >> >> -- >> --Guido van Rossum (python.org/~guido) >> *Pronouns: he/him **(why is my pronoun here?)* >> <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> >> _______________________________________________ >> 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/MXVBSNUTLVJVKWIVUK7MSCKM4YDPEL4Y/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > -- > Christopher Barker, PhD (Chris) > > Python Language Consulting > - Teaching > - Scientific Software Development > - Desktop GUI and Web Development > - wxPython, numpy, scipy, Cython > -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
_______________________________________________ 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/PODUQXNURYYPUJBBYS6T4O4X2XT3WOA2/ Code of Conduct: http://python.org/psf/codeofconduct/
