<s>[INST] Traverse a list in reverse order in Python So I can start from len(collection) and end in collection[0].
EDIT: Sorry, I forgot to mention I also want to be able to access the loop index.
 [/INST] Use the reversed() built-in function:
>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
...     print i
... 
baz
bar
foo

To also access the original index:
>>> for i, e in reversed(list(enumerate(a))):
...     print i, e
... 
2 baz
1 bar
0 foo

 </s>