I need to attribute ranks to elements of a list while making sure tied elements get the same rank.
For instance:
data = [[1],[3],[2],[2]]
c = 0
for i in sorted(data, reverse=True):
i.append(c+1)
c += 1
print data
returns:
[[1, 4], [3, 1], [2, 2], [2, 3]]
Where a rank is appended to the score.
What would I need to change to this simple code to instead obtain:
[[1, 3], [3, 1], [2, 2], [2, 2]]
Where elements scoring 2 are tied and both obtain the second place, while 1, the previously fourth place, is promoted to third place?
Using itertools.groupby, enumerate:
>>> from itertools import groupby
>>> data = [[1],[3],[2],[2]]
>>> sorted_data = sorted(data, reverse=True)
>>> for rank, (_, grp) in enumerate(groupby(sorted_data, key=lambda xs: xs[0]), 1):
... for x in grp:
... x.append(rank)
...
>>> print data
[[1, 3], [3, 1], [2, 2], [2, 2]]