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Sorry for the wordy and confusing title, I found it’s hard to describe what I wanted while trying to search for an existing answer on the Internet. I wanted a simpler code for merging two dict-type without looping. I didn’t find I wanted, so I wrote one on my own. To show you clearly, considering with only two dicts in Python 3:

from pprint import pprint

d1 = {'A': 1, 'B': 2}
d2 = {'A': 3, 'C': 4}

d = dict((key, (d1.get(key, 0), d2.get(key, 0))) \
         for key in d1.keys() | d2.keys())
pprint(d)

{'A': (1, 3), 'B': (2, 0), 'C': (0, 4)}

So, this should clarify. In Python 2.X, you need to explicitly use set-type for union operation on two dict-types keys:

from pprint import pprint

d1 = {'A': 1, 'B': 2}
d2 = {'A': 3, 'C': 4}

d = dict((key, (d1.get(key, 0), d2.get(key, 0))) \
         for key in set(d1.keys()) | set(d2.keys()))
pprint(d)

{'A': (1, 3), 'B': (2, 0), 'C': (0, 4)}

A key may not appear in the other dict-type, which is the case I have. Although I only need to merge two dict-types, but why not generalize it for arbitrary number of dict-types:

from pprint import pprint
import itertools
import random
import string

DICTS = 5
KEYPOOL= string.ascii_uppercase[:DICTS]
KEYS = 3

def random_dict(i):
  d = dict((key, random.randint(1, 10)) \
           for key in random.sample(KEYPOOL, KEYS))
  print('=== dict %d ===' % i)
  pprint(d)
  return d

dicts = [random_dict(i) for i in range(DICTS)]

d = dict((key, tuple(d.get(key, 0) for d in dicts)) for key in \
         set(itertools.chain.from_iterable(d.keys() for d in dicts)))
print('=== result ===')
pprint(d)

=== dict 0 ===
{'A': 4, 'B': 10, 'C': 8}
=== dict 1 ===
{'B': 5, 'C': 3, 'D': 3}
=== dict 2 ===
{'A': 8, 'D': 3, 'E': 10}
=== dict 3 ===
{'A': 7, 'C': 2, 'D': 10}
=== dict 4 ===
{'A': 8, 'C': 3, 'D': 6}
=== result ===
{'A': (4, 0, 8, 7, 8),
 'B': (10, 5, 0, 0, 0),
 'C': (8, 3, 0, 2, 3),
 'D': (0, 3, 3, 10, 6),
 'E': (0, 0, 10, 0, 0)}

It uses itertools.chain.from_iterable to chain all iterables from dict.keys(), then convert to set-type to remove duplicates. Generating a tuple-type with a generator which loops through all dict-types for values by key, then forming another tuple-type with the key, so it can be converted into an item of the final dict-type.

Note that the code use tuple-type to contains the values, not list-type as title says, that’s up to you, simply replace tuple-type with with list-type.