[issue30084] starred tuple expression vs list display and function call

[Steven D'Aprano]

Steven D'Aprano added the comment:

> list expression pass starred expression, the other hand
> tuple expression cannot pass starred expression.

You are misinterpreting what you are seeing.

( ) is not a tuple expression (except for the special case of empty brackets, which makes an empty tuple). It's just grouping an expression. So (*x) is equivalent to just bare *x.

To make a tuple, you need a comma.

Apart from the empty tuple, the brackets are just for grouping. Put a comma after the starred expression and it will work:

py> t = 1, 2
py> t
(1, 2)
py> (*t,)
(1, 2)


The trailing comma is allowed in lists as well:

py> [*t,]
[1, 2]


I agree with Martin: there's no bug here, the behaviour is consistent with the way tuples and lists are normally created, and there's no need to make (*t) yet another special case.

If you really want to argue in favour of this change, I suggest you discuss it on the Python-Ideas mailing list and see if you can get community consensus for it. *If* you get agreement that this is a good idea, then you can re-open this.

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nosy: +steven.daprano
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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<http://bugs.python.org/issue30084>
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