如何将字典列表转换为Python中的列表字典？

Question

It may be a classical question in Python, but I haven't found the answer yet.

I have a list of dictionaries, these dictionaries have similar keys. It looks like this:

 [{0: myech.MatchingResponse at 0x10d6f7fd0, 
   3: myech.MatchingResponse at 0x10d9886d0,
   6: myech.MatchingResponse at 0x10d6f7d90,
   9: myech.MatchingResponse at 0x10d988ad0},
  {0: myech.MatchingResponse at 0x10d6f7b10,
   3: myech.MatchingResponse at 0x10d6f7f90>}]

I would like to get a new dictionary with [0,3,6,9] as keys, and lists of " myech.MatchingResponse" as values.

Of course I can do this using a simple loop but I was wondering if there is a more efficient solution.

Answer 1

import collections

result = collections.defaultdict(list)

for d in dictionaries:
    for k, v in d.items():
        result[k].append(v)

Answer 2

let's say your list is assigned to a variable called mylist.

mydic = {}
for dic in mylist:
    for key, value in dic.items():
        if key in mydic:
            mydic[key].append(value)
        else:
            mydic[key] = [value]

Answer 3

It's possible to do this with dict comprehension as well ... could be one line, but I've kept it as two lines for clarity. :)

from itertools import chain

all_keys = set(chain(*[x.keys() for x in dd]))
print {k : [d[k] for d in dd if k in d] for k in all_keys}

Results in:

{0: ['a', 'x'], 9: ['d'], 3: ['b', 'y'], 6: ['c']}

Answer 4

If you have a list of dictionaries with identical keys in each, you can convert these to a dictionary of lists as in the following example, (which some would consider more pythonic than some of the other answers).

d = []
d.append({'a':1,'b':2})
d.append({'a':4,'b':3}) 
print(d)                                                               
[{'a': 1, 'b': 2}, {'a': 4, 'b': 3}]

newdict = {}
for k,v in d[0].items():
    newdict[k] = [x[k] for x in d]

print(newdict)
{'a': [1, 4], 'b': [2, 3]}