Iterating over sequence in reversed order

Use built-in function reversed() to iterate over a sequence in reversed order.

>>> l = [1, 2, 3, 4, 5]
>>> for i in reversed(l):
...    print(i)
...
5
4
3
2
1

The reverse iteration will only work if the object has a certain size or if a special __reversed__() method is implemented in it. If
none of these conditions are met, you will have to convert the object to a list first. For example:

# Prints lines in the file in reversed order
with open('somefile.txt') as f:
    for line in reversed(list(f)):
        print(line)

Note that converting an iterated object into a list can consume a lot of memory if the list is large.

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