[Tutor] Flatten a list in tuples and remove doubles

[eryksun]

On Sun, Jul 29, 2012 at 4:29 PM, Peter Otten <__peter__ at web.de> wrote:
>
> If you have to sort your data anyway you can sort it first and then apply
> itertools.groupby()...

That was my thinking. I wrote it with groupby (see link below) because
Francesco described field 0 as "in growing order".

http://mail.python.org/pipermail/tutor/2012-July/090607.html

I see now the 2nd call to sorted() in the tuple generator was
redundant. I should have just sorted the data without the key function
to order within each group by field 4 in the first pass:

keyfunc = itemgetter(0,1,2,3)
groups = groupby(sorted(data), keyfunc)

result = []
for group, records in groups:
    temp = tuple('%s/%s' % r[5:] for r in records)
    result.append(group + temp)

In general though you have to sort and group by the same key.