Asterisk in a tuple, list and many definitions, double asterisk in dict definition

Question

I am currently playing with the Python 3.5 interpreter and found a very interesting behavior:

>>> (1,2,3,"a",*("oi", "oi")*3)
(1, 2, 3, 'a', 'oi', 'oi', 'oi', 'oi', 'oi', 'oi')
>>> [1,2,3,"a",*range(10)]
[1, 2, 3, 'a', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> ('aw','aw',*range(10),*(x**2 for x in range(10)))
('aw', 'aw', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 4, 9, 16, 25, 36, 49, 64, 81)
>>> {"trali":"vali", **dict(q=1,p=2)}
{'q': 1, 'p': 2, 'trali': 'vali'}
>>> {"a",1,11,*range(5)}
{0, 1, 2, 3, 4, 11, 'a'}

I have never seen this either in the documentation, in the examples, or in any source code, despite several years of my Python experience. And I found it very useful.

And that seems logical to me in terms of Python grammar. Function arguments and a tuple can be parsed with the same or similar states.

Is this documented behavior? Where is this documented?

What versions of Python have this functionality?

Answer 1

PEP-448: , Python 3.5.

https://docs.python.org/3/whatsnew/3.5.html#pep-448-additional-unpacking-generalizations:

PEP 448 * ** . :

>>>

>>> print(*[1], *[2], 3, *[4, 5])
1 2 3 4 5

>>> def fn(a, b, c, d):
...     print(a, b, c, d)
...

>>> fn(**{'a': 1, 'c': 3}, **{'b': 2, 'd': 4})
1 2 3 4

, , , :

>>>

>>> *range(4), 4
(0, 1, 2, 3, 4)

>>> [*range(4), 4]
[0, 1, 2, 3, 4]

>>> {*range(4), 4, *(5, 6, 7)}
{0, 1, 2, 3, 4, 5, 6, 7}

>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}