asterisk in tuple, list and set definitions, double asterisk in dict definition

Question

I\'m playing now with Python 3.5 interpreter and found very interesting behavior:

>>> (1,2,3,\"a\",*(\"oi\", \"oi\")*3)
(1, 2, 3, \'a\', \'oi\', \'o         


        

Answer 1

This is PEP-448: Additional Unpacking Generalizations, which is new in Python 3.5.

The relevant change-log is in https://docs.python.org/3/whatsnew/3.5.html#pep-448-additional-unpacking-generalizations:

PEP 448 extends the allowed uses of the * iterable unpacking operator and ** dictionary unpacking operator. It is now possible to use an arbitrary number of unpackings in function calls:

>>>

>>> 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

Similarly, tuple, list, set, and dictionary displays allow multiple unpackings:

>>>

>>> *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}