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A new built-in function, reversed(seq), takes a sequence
and returns an iterator that loops over the elements of the sequence
in reverse order.
>>> for i in reversed(xrange(1,4)):
... print i
...
3
2
1
Compared to extended slicing, such as range(1,4)[::-1],
reversed() is easier to read, runs faster, and uses
substantially less memory.
Note that reversed() only accepts sequences, not arbitrary
iterators. If you want to reverse an iterator, first convert it to
a list with list().
>>> input = open('/etc/passwd', 'r')
>>> for line in reversed(list(input)):
... print line
...
root:*:0:0:System Administrator:/var/root:/bin/tcsh
...
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