I'm using Python 3.5.
As part of a problem, I'm trying to design a function that takes a list as input and reverts it. So if
x = [a, b, c]
x = [c, b, a]
for revert in range(1, len(x) + 1):
`y = x[::-1]`
def rev(l): r =  for i in l: r.insert(0, i) return r
By continuously inserting at the zero-th position you end up with a reversed version of the input list:
>>> print(rev([1, 2, 3, 4])) [4, 3, 2, 1]
def rev(l): return l[::-1]
could also be considered a solution.
:: has a different result) isn't a function (it's a slice) and
 is, again, a list method. Also, contrasting
insert, it is faster and way more readable; just make sure you're able to understand and explain it. A nice explanation of how it works can be found in this S.O answer.
*Reeaaalllyyyy slow, see juanpa.arrivillaga's answer for cool graph