Is there a way to check if elements in sub list are equall in any of the other sublists-CodePudding

So i have a list with 1000 sub-list where the sub-lists have a date in this format "2022-01-01" and an index to another list. So the list loks like this [["2022-01-01", 3], ["2010-01-01", 1], ["2022-01-01", 12]] with 1000 elements.

What i would like to get is a new list with sub-list that have the index of the dates that are equal.

So the output should look like this [[3, 12,]].

I have try'd

count = 0
for i in range(len(dateList)):
    if i != x:
        if dateList[i][0] == dateList[x][0]:
            print(dateList[i][0], dateList[x][0])
    count  = 1

for i in range(len(dateList)):
    for x in range(len(dateList)):
       if 1!= x:  
         if dateList[i][0] == dateList[x][0]:
            print(dateList[i][0], dateList[x][0])

I understand why both are wrong, I used them to try to get my thoughts to the rigth answer. However I cant seem to find any solution.

CodePudding user response：

You can use a defaultdict to create a data structure keyed by the dates and whose values are the indices where those dates occur. Once you create such a thing, you can iterate over its values, selecting the ones which have more than one entry:

from collections import defaultdict

date_list = [["2022-01-01", 3], ["2010-01-01", 1], ["2022-01-01", 12]]

d = defaultdict(list)

for i,date_pair in enumerate(date_list):
    date = date_pair[0]
    d[date].append(i)

duplicates = [v for v in d.values() if len(v) > 1]

print(duplicates) #[[0,2]]