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"Data blocks" syntax specification draft

Am 23.05.18 um 07:22 schrieb Chris Angelico:
> On Wed, May 23, 2018 at 9:51 AM, bartc <bc at 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:


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.