list replacer.py

from collections import OrderedDict
import csv

mainlist = []

fn = open('Finland_Day1_Conflict-Names.csv', 'r')
day1 = csv.reader(fn)
for row in day1:
    mainlist.append([row[1],row[2]])
fn.close()

replacements = []
references = []

fn = open('Finland_Day2_Conflict-Names.csv', 'r')
day2 = csv.reader(fn)
for row in day2:
    replacements.append(row[0])
    references.append(row[1])
fn.close()

replacements_split = [replacements[x:x+2] for x in range(0, len(replacements), 2)]
references_split = [references[x:x+2] for x in range(0, len(references), 2)]
merged = [x + y for x,y in zip(replacements_split,references_split)]

maindct = []
replacedct = []
output_list = []

maindct = OrderedDict((frozenset(item[:2]),item[2:]) for item in mainlist)
replacedct = {frozenset(item[:2]):item[2:] for item in merged}

# Now it is trivial to create another dict with the desired output:
output_list = [replacedct[key] + maindct[key] for key in maindct]

print(output_list)