On Wed, May 23, 2018 at 12:01 AM, Ian Kelly <ian.g.ke...@gmail.com> wrote: > On Tue, May 22, 2018 at 11:32 PM, Christian Gollwitzer <aurio...@gmx.de> > wrote: >> Am 23.05.18 um 07:22 schrieb Chris Angelico: >>> >>> On Wed, May 23, 2018 at 9:51 AM, bartc <b...@freeuk.com> wrote: >>>> >>>> Sorry, but I don't think you're right at all. unless the official >>>> references >>>> for the language specifically say that commas are primarily for >>>> constructing >>>> tuples, and all other uses are exceptions to that rule. >>> >>> >>> "A tuple consists of a number of values separated by commas" >>> >>> https://docs.python.org/3/tutorial/datastructures.html#tuples-and-sequences >>> >>> "Separating items with commas" >>> https://docs.python.org/3/library/stdtypes.html#tuple >>> >>> "Note that tuples are not formed by the parentheses, but rather by use >>> of the comma operator." >>> https://docs.python.org/3/reference/expressions.html#parenthesized-forms >>> >>> Enough examples? Commas make tuples, unless context specifies otherwise. >> >> >> I'd think that the definitive answer is in the grammar, because that is what >> is used to build the Python parser: >> >> https://docs.python.org/3/reference/grammar.html >> >> Actually, I'm a bit surprised that tuple, list etc. does not appear there as >> a non-terminal. It is a bit hard to find, and it seems that "atom:" is the >> starting point for parsing tuples, lists etc. > > For enclosed tuples, yes. I believe that tuples without parentheses > can be produced by either 'exprlist' or 'testlist' (which is why some > cases permit iterable unpacking and some don't).
Er, that should be "either 'testlist_star_expr' or 'testlist'". -- https://mail.python.org/mailman/listinfo/python-list
