按 Python 列表列表中的项目分组

Grouping by items in list of lists in Python

我有一个 Python 列表,如下所示:

mylist = [[1,apple,orange,banana],[2,apple],[3,banana,grapes]]

我怎样才能把它变成这样的东西:

new_list = [[apple,1,2],[orange,1],[banana,1,3],[grapes,3]

基本上我想创建新的列表列表,该列表按原始列表列表中的每个水果分组,第一个索引中有数字

您可以使用 defaultdict 对每个水果的索引进行分组,然后连接键和值

from collections import defaultdict
mylist = [[1, "apple", "orange", "banana"], [2, "apple"], [3, "banana", "grapes"]]

result = defaultdict(list)
for idx, *fruits in mylist:
    for fruit in fruits:
        result[fruit].append(idx)
print(result)  # {'apple': [1, 2], 'orange': [1], 'banana': [1, 3], 'grapes': [3]}

result = [[key, *values] for key, values in result.items()]
print(result)  # [['apple', 1, 2], ['orange', 1], ['banana', 1, 3], ['grapes', 3]]