如何在python字典中组合公共键和连接值

Question

我有一张单子，里面有几本字典。你知道吗

   [{u'TEXT242.txt': u'work'},{u'TEXT242.txt': u'go to work'},{u'TEXT1007.txt': u'report'},{u'TEXT797.txt': u'study'}]

当字典有相同的键时如何组合它。例如： u'work'，u'go to work'在一个键下：'TEXT242.txt'，这样我就可以删除重复的键。你知道吗

 [{u'TEXT242.txt': [u'work', u'go to work']},{u'TEXT1007.txt': u'report'},{u'TEXT797.txt': u'study'}]

Answer 1

字典的setdefault方法在这里很方便。。。它可以在字典键不存在时创建一个空列表，这样您就可以随时追加值。你知道吗

dictlist = [{u'TEXT242.txt': u'work'},{u'TEXT242.txt': u'go to work'},{u'TEXT1007.txt': u'report'},{u'TEXT797.txt': u'study'}]
newdict = {}

for d in dictlist:
    for k in d:
        newdict.setdefault(k, []).append(d[k])

Answer 2

from collections import defaultdict
before = [{u'TEXT242.txt': u'work'},{u'TEXT242.txt': u'go to work'},{u'TEXT1007.txt': u'report'},{u'TEXT797.txt': u'study'}]
after = defaultdict(list)
for i in before:
    for k, v in i.items():
        after[k].append(v)

输出：

defaultdict(list,
            {'TEXT1007.txt': ['report'],
             'TEXT242.txt': ['work', 'go to work'],
             'TEXT797.txt': ['study']})

This technique is simpler and faster than an equivalent technique using dict.setdefault()