How to find common keys in a list of dicts and sort them by value?

问题

I want to create a finalDic which contains common keys and sum of their values

myDic = [{2:1, 3:1, 5:2}, {3:4, 6:4, 2:3}, {2:5, 3:6}, ...]

First find common keys

commonkey = [{2:1, 3:1}, {2:3, 3:4}, {2:5, 3:6}]

Then Sum and sort by their values

finalDic= {3:11, 2,9}

I've tried this and not even close what i want

import collections

myDic = [{2:1, 3:1, 5:2}, {3:4, 6:4, 2:3}, {2:5, 3:6}]

def commonKey(x):
    i=0
    allKeys = []
    while i<len(x):
        for key in x[0].keys():
            allKeys.append(key)
        i=i+1
    commonKeys = collections.Counter(allKeys)
    commonKeys = [i for i in commonKeys if commonKeys[i]>len(x)-1]
    return commonKeys

print commonKey(myDic)

Thanks

回答1:

Here's how I'd do it:

my_dict = [{2:1, 3:1, 5:2}, {3:4, 6:4, 2:3}, {2:5, 3:6}]

# Finds the common keys
common_keys = set.intersection(*map(set, my_dict))

# Makes a new dict with only those keys and sums the values into another dict
summed_dict = {key: sum(d[key] for d in my_dict) for key in common_keys}

Or as a crazy one-liner:

{k: sum(d[k] for d in my_dict) for k in reduce(set.intersection, map(set, my_dict))}

回答2:

Only some pointers:

obtain the keys from each directory in turn them into a set() and calculate the intersection() or all key sets. This will give you the common keys.
now iterating over the original data and summing up the matching values from each dict is straight forward

The implementation is left to the OP as an exercise.

回答3:

l = [{2:1, 3:1, 5:2}, {3:4, 6:4, 2:3}, {2:5, 3:6}]

new_dict = {}

def unique_key_value(a,b):
    return set(a).intersection(set(b))

def dict_sum(k, v):
    if k not in new_dict.keys():
        new_dict[k] = v
    else:
        new_dict[k] = new_dict[k] + v

for i in reduce(unique_key_value, l):
    for k in l:
        if i in k.keys():
            dict_sum(i, k[i])

print new_dict

hope this helps. :)

回答4:

python 3.2

from collections import defaultdict
c=defaultdict(list)
for i in myDic:
     for m,n in i.items():
            c[m].append(n)
new_dic={i:sum(v) for i,v in c.items()if len(v)==len(myDic)}
print(new_dic)

来源：https://stackoverflow.com/questions/13985686/how-to-find-common-keys-in-a-list-of-dicts-and-sort-them-by-value

标签

python

list

sorting

dictionary