python - Python - 从列表中识别子列表项重复的项

Question

糟糕的标题，请酌情重命名或概括。

设想：

inputList = [[1, "Data x"], [2, "Data z"], [3, "Data x"]]

我想找到索引 [1] 的重复项。

DesiredOutput = [[1, "Data x"], [3, "Data x"]]

理想情况下， [1] 将是另一个列表，而不是字符串：

[[1, ["Data x1", "Data x2"], [2,  ["Data x1", "Data x2"]]

Answer 1

怎么样（只是一种选择）

inputList = [[1, "Data x"], [2, "Data z"], [3, "Data x"]]

from operator import itemgetter
from collections import defaultdict

dd = defaultdict(list)
for i, v in enumerate(inputList):
    dd[v[1]].append(i)

dupes = [itemgetter(*v)(inputList) for v in dd.itervalues() if len(v) > 1]
# [([1, 'Data x'], [3, 'Data x'])]

Answer 2

inputList = [[1, "Data x"], [2, "Data z"], [3, "Data x"]]

DesiredOutput = [] # Create empty list

for x in inputList:  
    if x[1] == inputList[0][1]: #compare reference value with each item in inputList 
        DesiredOutput.append(x)  
print(DesiredOutput)

#[[1, "Data x"], [3, "Data x"]]

Answer 3

在这里使用字典：

>>> inputList = [[1, "Data x"], [2, "Data z"], [3, "Data x"]]
>>> from collections import defaultdict
>>> dic = defaultdict(list)
>>> for v, k in inputList:
...     dic[k].append(v)
...     
>>> dic
defaultdict(<type 'list'>, {'Data z': [2], 'Data x': [1, 3]})

由于第二个示例中的项目是列表，因此您需要先将它们转换为元组：

for v, k in inputList:
   dic[tuple(k)].append(v)

Answer 4

input_list = [[1, "Data x"], [2, "Data z"], [3, "Data x"]]
desired_output = [x for x in input_list if x[1] == input_list[0][1]]
print(desired_output)