How can I group equivalent items together in a Python list?

Question

I have a list like

x = [2, 2, 1, 1, 1, 1, 1, 1]

I would like to put the repeated numbers together like

[[2,2],[1,1,1,1,1,1]] 

Answer 1

[list(g) for k, g in itertools.groupby(iterable)]

This is exactly what itertools.groupby is for.

If you want nonconsecutive numbers grouped, like in the comment by @Michal,

[list(g) for k, g in itertools.groupby(sorted(iterable))]