Unpacking in comprehensions

This is another long-requested feature. If you wanted to completely unpack or “flatten” a nested object using a comprehension, you used to need a function like itertools.chain() or you would have to write a nested comprehension with an ugly syntax:

x = [[1,2,3],[4,5],[6]]
y = [a for b in x for a in b]
>>> [1, 2, 3, 4, 5, 6] # y

Unpacking in comprehensions using the star operator lets you save yourself a step:

x = [[1,2,3],[4,5],[6]]
y = [*a for a in x]
>>> [1, 2, 3, 4, 5, 6] # y

Unpacking with ** also works, for instance as a way to flatten and combine dictionaries: