根据python中其他列表的值获取max子列表

Question

want to get sublist which has max value on specified index based on condition.

mainlist=[[['RD-2', 'a', 120], ['RD-2', 'b', 125], ['RD-2', 'c', 127]], [['RD-3', 'a', 120], ['RD-3', 'b', 140]], [['RD-5', 'a', 120]],[['RD-7', 'a', 122]]]

and another list

baselist=[['RD-2', 100],['RD-3', 200],['RD-5', 240]]

for every first sub-element in baselist, i need the 1 complete sublist from mainlist which has max value in 2nd index position. the output should be

flist=[['RD-2', 'c', 127],['RD-3', 'b', 140],['RD-5', 'a', 120]]

help me.

Answer 1

Try this:

flist = []               
for item in baselist: 
     for i in mainlist:       
         if i[0][0] ==item[0]:               
             flist.append(max(i, key=lambda x:x[2]))

the flist will be:

[['RD-2', 'c', 127], ['RD-3', 'b', 140], ['RD-5', 'a', 120]]

you can also use itertools.product to simplyfy for loops a little:

from itertools import product    

flist = []               
for i, item in product(mainlist,baselist):      
     if i[0][0] ==item[0]:               
          flist.append(max(i, key=lambda x:x[2]))

or also in just one line:

flist = [max(i, key=lambda x:x[2]) for i, item in product(mainlist,baselist) if i[0][0] == item[0]]

Answer 2

A bit more compact but with the same outcome using list comprehension:

max_entries = [max(x, key=lambda x:x[2]) for x in mainlist]
flist = [max_entry for max_entry in max_entries for base_entry in baselist if max_entry[0]==base_entry[0]]

Answer 3

Here's a way using a list comprehension:

base = list(zip(*baselist))[0]
[max(i, key=lambda x:x[2]) for i in mainlist if i[0][0] in base]
[['RD-2', 'c', 127], ['RD-3', 'b', 140], ['RD-5', 'a', 120]]

Answer 4

I would first store you max lists in a dictionary, then just reference that dictionary later to build the new list:

from operator import itemgetter

mainlist = [
    [["RD-2", "a", 120], ["RD-2", "b", 125], ["RD-2", "c", 127]],
    [["RD-3", "a", 120], ["RD-3", "b", 140]],
    [["RD-5", "a", 120]],
    [["RD-7", "a", 122]],
]

baselist = [["RD-2", 100], ["RD-3", 200], ["RD-5", 240]]

d = {}
for sublist in mainlist:
    k = sublist[0][0]
    d[k] = max(sublist, key=itemgetter(2))

flist = [d.get(k) for k, _ in baselist]

print(flist)
# [['RD-2', 'c', 127], ['RD-3', 'b', 140], ['RD-5', 'a', 120]]