python - 根据元素名称在python中对长列表的元素进行分组

Question

我有一个长长的列表，如下所示，我分别根据(元素[0]、元素[3]、元素[2])对它们进行了排序。对于元素，我的意思是下划线之间的数字。

list3=['20180406_145813_4_1.jpg',
 '20180406_145813_5_1.jpg',
 '20180406_145813_6_1.jpg',
 '20180406_175827_10_12.jpg',
 '20180406_175827_11_12.jpg',
 '20180409_190651_7_2.jpg',
 '20180409_190651_8_2.jpg',
...]

现在，我想根据元素[3]拆分列表。我想要的结果是:

[['20180406_145813_4_1.jpg',
 '20180406_145813_5_1.jpg',
 '20180406_145813_6_1.jpg'],
 ['20180406_175827_10_12.jpg',
 '20180406_175827_11_12.jpg'],
 ['20180409_190651_7_2.jpg',
 '20180409_190651_8_2.jpg'],
...]

我有这段代码可以将每个名字打印成一个列表。我不知道如何在这段代码中按 element3 分组:

for imagename in list3:
    element3 = imagename.split("_")[3]
    for j,m in groupby(list3):
        print(list(m))

Answer 1

您可以使用 itertools.groupby像这样:

from itertools import groupby

list3 = ['20180406_145813_4_1.jpg',
         '20180406_145813_5_1.jpg',
         '20180406_145813_6_1.jpg',
         '20180406_175827_10_12.jpg',
         '20180406_175827_11_12.jpg',
         '20180409_190651_7_2.jpg',
         '20180409_190651_8_2.jpg']

result = [list(group) for _, group in groupby(list3, key=lambda x: x.split('_')[3])]
print(result)

输出

[['20180406_145813_4_1.jpg', '20180406_145813_5_1.jpg', '20180406_145813_6_1.jpg'], ['20180406_175827_10_12.jpg', '20180406_175827_11_12.jpg'], ['20180409_190651_7_2.jpg', '20180409_190651_8_2.jpg']]

以上list comprehension等同于以下 for 循环:

result = []
for _, group in groupby(list3, key=lambda x: x.split('_')[3]):
    result.append(list(group))