On Mon, May 31, 2021 at 2:40 PM Guido van Rossum <gu...@python.org> wrote:
> Andre, did you have an experience where something related to Ellipsis/... > confused you? It is not clear to me what exactly prompted you to single out > Ellipsis (or it’s repr()?) > Guido, the reason why I tried is that I am working on a project called friendly (previously named friendly-traceback) which aims to provide "easy to understand" explanations to beginners when they encounter tracebacks.[1] In playing with different cases involving assignments to a constant (__debug__, None, True, False, ... and Ellipsis as '...'), I came across this particular case which I thought was confusing: Python says that we cannot assign to Ellipsis ... and yet we can. I thought that the explanation provided by cPython itself could be made a bit clearer. The specific suggestion I made is based on the explanation *friendly* currently gives, where it specifies that Ellipsis refers to (...). Admittedly, this is rather a corner case. André ==== With friendly, I usually strive to cover more typical cases that are encountered by beginners, such as one example I gave at this year's PyConUS Education summit where, given the following message: AttributeError: partially initialized module 'turtle' has no attribute 'forward' (most likely due to a circular import) friendly adds the following "hint": Did you give your program the same name as a Python module? And, upon being prompted, friendly adds the following: I suspect that you used the name turtle.py for your program and that you also wanted to import a module with the same name from Python's standard library. If so, you should use a different name for your program. (This particular turtle is not hard-coded in friendly; any circular import is similarly analyzed and some further explanation is provided.) [1] Currently, I have at least 150 different cases yielding SyntaxErrors for which friendly can provide help (see https://aroberge.github.io/friendly-traceback-docs/docs/html/syntax_tracebacks_en_3.8.html for cases covered by unit tests) and probably a hundred or so of various types of other errors. Furthermore, friendly is designed so that the explanations can be translated into other languages; currently, every case friendly covers has explanations available in both English and French. > On Mon, May 31, 2021 at 08:37 André Roberge <andre.robe...@gmail.com> > wrote: > >> >> >> On Mon, May 31, 2021 at 12:20 PM MRAB <pyt...@mrabarnett.plus.com> wrote: >> >>> On 2021-05-31 15:55, Paul Bryan wrote: >>> > If you're proposing prevention of monkey patching Ellipsis, I think >>> > you'll have to go all-in on all builtins. >>> > >>> > For example: >>> > >>> >>>> str = int >>> > >>> >>>> str >>> > >>> > <class 'int'> >>> > >>> >>>> str == int >>> > >>> > True >>> > >>> > >>> If you rebind str to int, the repr of str will say <class 'int'>, so you >>> can tell that something's happened, but the repr of ... is always >>> 'Ellipsis', even though you've rebound Ellipsis. >>> >> >> Exactly. >> >> Thinking some more about it, perhaps the confusion would be sufficiently >> reduced if the repr of '...' would be 'Ellipsis (...)', and use this repr >> to appear in error messages rather than simply the name Ellipsis. >> >> >> >>> >>> > >>> > On Mon, 2021-05-31 at 11:37 -0300, André Roberge wrote: >>> >> In Python `...` is referred to as `Ellipsis` and cannot be assigned >>> to. >>> >> Yet, one can assign any value to the name `Ellipsis`. >>> >> >>> >> Consider the following: >>> >> >>> >> ``` >>> >> >>> ... >>> >> Ellipsis >>> >> >>> ... == Ellipsis >>> >> True >>> >> >>> Ellipsis >>> >> Ellipsis >>> >> >>> Ellipsis = 3 >>> >> >>> Ellipsis >>> >> 3 >>> >> >>> ... = 4 >>> >> File "<stdin>", line 1 >>> >> ... = 4 >>> >> ^ >>> >> SyntaxError: cannot assign to Ellipsis >>> >> >>> # But I just did assign a new value to the name Ellipsis above. >>> >> >>> Ellipsis >>> >> 3 >>> >> >>> ... >>> >> Ellipsis >>> >> >>> ... == Ellipsis >>> >> False >>> >> ``` >>> >> >>> >> For consistency, `Ellipsis` (the name) should **always** refer to the >>> >> same object that `...` refers to, so that both could not be assigned >>> a >>> >> new value. >>> >> >>> _______________________________________________ >>> 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/NE2FAW3XDFYUIMILV4BC2XT6VKLC4P6V/ >>> Code of Conduct: http://python.org/psf/codeofconduct/ >>> >> _______________________________________________ >> 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/DIRDIQFK72LFHYJNAD5BWL3L5SPAUMVM/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > -- > --Guido (mobile) >
_______________________________________________ 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/VWKCMABYL3B4VMN22I7HYEYJOITUOQPV/ Code of Conduct: http://python.org/psf/codeofconduct/
