Core Python Programming (2nd Edition)

There is a reversed() built-in function that returns an iterator that traverses an iterable in reverse order.
The enumerate() BIF also returns an iterator. Two new BIFs, any() and all(), made their debut in Python
2.5they will return true if any or all items traversed across an iterator have a Boolean true value,
respectively. We saw earlier in the chapter how you can use it in a for loop to iterate over both the
index and the item of an iterable. There is also an entire module called itertools that contains various
iterators you may find useful.
8.11.4. Using Iterators with ...
Sequences
As mentioned before, iterating through Python sequence types is as expected:
>>> myTuple = (123, 'xyz', 45.67)
>>> i = iter(myTuple)
>>> i.next()
123
>>> i.next()
'xyz'
>>> i.next()
45.67
>>> i.next()
Traceback (most recent call last):
File "", line 1, in ?
StopIteration
If this had been an actual program, we would have enclosed the code inside a try-except block.
Sequences now automatically produce their own iterators, so a for loop:
for i in seq:
do_something_to(i)
under the covers now really behaves like this:
fetch = iter(seq)
while True:
try:
i = fetch.next()
except StopIteration:
break
do_something_to(i)
However, your code does not need to change because the for loop itself calls the iterator's next()
method (as well as monitors for StopIteration).