On Sat, Jul 13, 2019 at 09:59:16AM +1000, Cameron Simpson wrote:
> Mike has probably confused this with tuples. Because tuples are
> delineated with parentheses, there is ambiguity between a tuple's
> parentheses and normal "group these terms together" parentheses.
There are no "tuple parentheses". Tuples are created by the *comma*,
not the parens. The only exception is the empty tuple, since you can't
have a comma on its own.
x = () # Zero item tuple.
x = 1, # Single item tuple.
x = 1, 2 # Two item tuple.
Any time you have a tuple, you only need to put parens around it to
dismbiguate it from the surrounding syntax:
x = 1, 2, (3, 4, 5), 6 # Tuple containing a tuple.
function(0, 1, (2, 3), 4) # Tuple as argument to a function.
or just to make it more clear to the human reader.
> Here is a 2 element tuple:
>
> (9, 7)
>
> How does one write a one element tuple? Like this:
>
> (9,)
To be clear, in both cases you could drop the parentheses and still get
a tuple:
9, 7
9,
provided that wasn't in a context where the comma was interpreted as
something with higher syntactic precedence, such as a function call:
func(9, 7) # Two integer arguments, not one tuple argument.
func((9, 7)) # One tuple argument.
--
Steven
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