For a given list of tuples, if multiple tuples in the list have the first element of tuple the same - among them select only the tuple with the maximum last element.
For example:
sample_list = [(5,16,2),(5,10,3),(5,8,1),(21,24,1)]
In the sample_list above since the first 3 tuples has the similar first element 5 in this case among them only the 2nd tuple should be retained since it has the max last element => 3.
Expected op:
op = [(5,10,3),(21,24,1)]
Code:
op = []
for m in range(len(sample_list)):
li = [sample_list[m]]
for n in range(len(sample_list)):
if(sample_list[m][0] == sample_list[n][0]
and sample_list[m][2] != sample_list[n][2]):
li.append(sample_list[n])
op.append(sorted(li,key=lambda dd:dd[2],reverse=True)[0])
print (list(set(op)))
This works. But it is very slow for long list. Is there a more pythonic or efficient way to do this?
Use itertools.groupby and operator.itemgetter for readability. Within the groups, apply max with an appropriate key function, again using itemgetter for brevity:
from itertools import groupby
from operator import itemgetter as ig
lst = [(5, 10, 3), (21, 24, 1), (5, 8, 1), (5, 16, 2)]
[max(g, key=ig(-1)) for _, g in groupby(sorted(lst), key=ig(0))]
# [(5, 10, 3), (21, 24, 1)]
For a linear-time solution, with extra-space only bound the number of unique first elements, you may use a dict:
d = {}
for tpl in lst:
first, *_, last = tpl
if first not in d or last > d[first][-1]:
d[first] = tpl
[*d.values()]
# [(5, 10, 3), (21, 24, 1)]
Try itertools.groupby:
from itertools import groupby
sample_list.sort()
print([max(l, key=lambda x: x[-1]) for _, l in groupby(sample_list, key=lambda x: x[0])])
Or also with operator.itemgetter:
from itertools import groupby
from operator import itemgetter
sample_list.sort()
print([max(l, key=itemgetter(-1)) for _, l in groupby(sample_list, key=itemgetter(0))])
For performance try:
from operator import itemgetter
dct = {}
for i in sample_list:
if i[0] in dct:
dct[i[0]].append(i)
else:
dct[i[0]] = [i]
print([max(v, key=itemgetter(-1)) for v in dct.values()])
All output:
[(5, 10, 3), (21, 24, 1)]