Python 联接-嵌套列表中的重复项

输出类似于：

for x in mylist:
        print x

我怎样才能使它在同一日期的副本连接在一起

例如，我希望它的输出是：

['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'R']
['2009/09/13_00:00', 'J']
['2009/09/13_00:00', 'J']
['2009/09/16_00:00', 'R']
['2009/09/18_00:00', 'R']
['2009/09/19_00:00', 'R']
['2009/09/23_00:00', 'R']
['2009/09/24_00:00', 'R']
['2009/09/24_00:00', 'W']
['2009/09/24_00:00', 'S']
['2009/09/24_00:00', 'S']
['2009/09/24_00:00', 'T']

我正试着画出这个

---

感谢您的帮助。

或者更明确地说，使用字典：收集日期和字母作为键，并跟踪字母出现的次数：

['2009/09/13_00:00', 'R, R, R, R, R, R']
['2009/09/13_00:00', 'J, J']
['2009/09/16_00:00', 'R']
['2009/09/18_00:00', 'R']
['2009/09/19_00:00', 'R']
['2009/09/23_00:00', 'R']
['2009/09/24_00:00', 'R']
['2009/09/24_00:00', 'W']
['2009/09/24_00:00', 'S, S']
['2009/09/24_00:00', 'T']

输出

：

mylist= [['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'J'],
         ['2009/09/13_00:00', 'J'],
         ['2009/09/16_00:00', 'R'],
         ['2009/09/18_00:00', 'R'],
         ['2009/09/19_00:00', 'R'],
         ['2009/09/23_00:00', 'R'],
         ['2009/09/24_00:00', 'R'],
         ['2009/09/24_00:00', 'W'],
         ['2009/09/24_00:00', 'S'],
         ['2009/09/24_00:00', 'S'],
         ['2009/09/24_00:00', 'T'],
        ]

for i in list(set([ tuple(i) for i in mylist])):
    print [list(i) +[list(i)[-1]] * (mylist.count(list(i))-1) ]

mylist= [['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'R'],
         ['2009/09/13_00:00', 'J'],
         ['2009/09/13_00:00', 'J'],
         ['2009/09/16_00:00', 'R'],
         ['2009/09/18_00:00', 'R'],
         ['2009/09/19_00:00', 'R'],
         ['2009/09/23_00:00', 'R'],
         ['2009/09/24_00:00', 'R'],
         ['2009/09/24_00:00', 'W'],
         ['2009/09/24_00:00', 'S'],
         ['2009/09/24_00:00', 'S'],
         ['2009/09/24_00:00', 'T'],
        ]

for i in list(set([ tuple(i) for i in mylist])):
    print [list(i) +[list(i)[-1]] * (mylist.count(list(i))-1) ]

[['2009/09/13_00:00', 'R', 'R', 'R', 'R', 'R', 'R']]
[['2009/09/16_00:00', 'R']]
[['2009/09/24_00:00', 'T']]
[['2009/09/24_00:00', 'S', 'S']]
[['2009/09/13_00:00', 'J', 'J']]
[['2009/09/24_00:00', 'R']]
[['2009/09/18_00:00', 'R']]
[['2009/09/19_00:00', 'R']]
[['2009/09/23_00:00', 'R']]
[['2009/09/24_00:00', 'W']]