For the first question, the first thing you should do is sort the list by the second field using itemgetter from the operator module:
x = [ ['4', '21', '1', '14', '2008-10-24 15:42:58'], ['3', '22', '4', '2somename', '2008-10-24 15:22:03'], ['5', '21', '3', '19', '2008-10-24 15:45:45'], ['6', '21', '1', '1somename', '2008-10-24 15:45:49'], ['7', '22', '3', '2somename', '2008-10-24 15:45:51'] ] from operator import itemgetter x.sort(key=itemgetter(1))
Then you can use itertools’ groupby function:
from itertools import groupby y = groupby(x, itemgetter(1))
Now y is an iterator containing tuples of (element, item iterator). It’s more confusing to explain these tuples than it is to show code:
for elt, items in groupby(x, itemgetter(1)): print(elt, items) for i in items: print(i)
Which prints:
21 <itertools._grouper object at 0x511a0> ['4', '21', '1', '14', '2008-10-24 15:42:58'] ['5', '21', '3', '19', '2008-10-24 15:45:45'] ['6', '21', '1', '1somename', '2008-10-24 15:45:49'] 22 <itertools._grouper object at 0x51170> ['3', '22', '4', '2somename', '2008-10-24 15:22:03'] ['7', '22', '3', '2somename', '2008-10-24 15:45:51']
For the second part, you should use list comprehensions as mentioned already here:
from pprint import pprint as pp pp([y for y in x if y[3] == '2somename'])
Which prints:
[['3', '22', '4', '2somename', '2008-10-24 15:22:03'], ['7', '22', '3', '2somename', '2008-10-24 15:45:51']]