在Python中对嵌套列表进行排序和分组

对于第一个问题,您应该做的第一件事是使用来自运算符模块的itemgetter按第二个字段对列表进行排序:

x = [
 ['4', '21', '1', '14', '2008-10-24 15:42:58'], 
 ['3', '22', '4', '2somename', '2008-10-24 15:22:03'], 
 ['5', '21', '3', '19', '2008-10-24 15:45:45'], 
 ['6', '21', '1', '1somename', '2008-10-24 15:45:49'], 
 ['7', '22', '3', '2somename', '2008-10-24 15:45:51']
]

from operator import itemgetter

x.sort(key=itemgetter(1))

然后你可以使用itertools的groupby函数:

from itertools import groupby
y = groupby(x, itemgetter(1))

现在y是一个包含元组(元素,项迭代器)的迭代器.解释这些元组比显示代码更令人困惑:

for elt, items in groupby(x, itemgetter(1)):
    print(elt, items)
    for i in items:
        print(i)

哪个印刷品:

21 
['4', '21', '1', '14', '2008-10-24 15:42:58']
['5', '21', '3', '19', '2008-10-24 15:45:45']
['6', '21', '1', '1somename', '2008-10-24 15:45:49']
22 
['3', '22', '4', '2somename', '2008-10-24 15:22:03']
['7', '22', '3', '2somename', '2008-10-24 15:45:51']

对于第二部分,您应该使用已在此处提到的列表推导:

from pprint import pprint as pp
pp([y for y in x if y[3] == '2somename'])

哪个印刷品:

[['3', '22', '4', '2somename', '2008-10-24 15:22:03'],
 ['7', '22', '3', '2somename', '2008-10-24 15:45:51']]

如果你把它分配给var"a"......

python 2.x:

#1:

a.sort(lambda x,y: cmp(x[1], y[1]))

#2:

filter(lambda x: x[3]=="2somename", a)

python 3:

#1:

a.sort(key=lambda x: x[1])