Traverse a list in reverse order in Python

You can do:

for item in my_list[::-1]:
    print item

(Or whatever you want to do in the for loop.)

The [::-1] slice reverses the list in the for loop (but won't actually modify your list "permanently").

Use the built-in reversed() function:

>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
...     print(i)
... 
baz
bar
foo

To also access the original index, use enumerate() on your list before passing it to reversed():

>>> for i, e in reversed(list(enumerate(a))):
...     print(i, e)
... 
2 baz
1 bar
0 foo

Since enumerate() returns a generator and generators can't be reversed, you need to convert it to a list first.

It can be done like this:

for i in range(len(collection)-1, -1, -1):
    print collection[i]

    # print(collection[i]) for python 3. +

So your guess was pretty close :) A little awkward but it's basically saying: start with 1 less than len(collection), keep going until you get to just before -1, by steps of -1.

Fyi, the help function is very useful as it lets you view the docs for something from the Python console, eg:

help(range)