On Wed, May 23, 2018 at 1:43 AM, Ian Kelly <ian.g.ke...@gmail.com> wrote: > On Tue, May 22, 2018 at 9:34 AM, Chris Angelico <ros...@gmail.com> wrote: >> On Wed, May 23, 2018 at 1:22 AM, Ian Kelly <ian.g.ke...@gmail.com> wrote: >>> On Tue, May 22, 2018 at 8:25 AM, Chris Angelico <ros...@gmail.com> wrote: >>>> On Tue, May 22, 2018 at 8:25 PM, bartc <b...@freeuk.com> wrote: >>>>> Note that Python tuples don't always need a start symbol: >>>>> >>>>> a = 10,20,30 >>>>> >>>>> assigns a tuple to a. >>>> >>>> The tuple has nothing to do with the parentheses, except for the >>>> special case of the empty tuple. It's the comma. >>> >>> Although, if the rule were really as simple as "commas make tuples", >>> then this would be a list containing a tuple: [1, 2, 3]. >> >> In an arbitrary expression, a comma between two expressions creates a >> tuple. In other contexts, the comma has other meanings, which take >> precedence: >> >> * Separating a function's arguments (both at definition and call) >> * Enumerating import targets and global/nonlocal names >> * Separating an assertion from its message >> * Listing multiple context managers >> * And probably some that I've forgotten. >> >> In those contexts, you can override the normal interpretation and >> force the tuple by using parentheses, preventing it from being parsed >> as something else, and making it instead a single expression: >> >> print((1, 2)) # prints a tuple >> print(1, 2) # prints two items >> >> The comma is what makes the tuple, though, not the parentheses. The >> parentheses merely prevent this from being something else. > > In other words, the rule is not really as simple as "commas make > tuples". I stand by what I wrote.
Neither of us is wrong here. "Commas make tuples" is a useful oversimplification in the same way that "asterisk means multiplication" is. The asterisk has other meanings in specific contexts (eg unpacking), but outside of those contexts, it means multiplication. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
