在不使用Counter的情况下合并python字典中的值

Question

I am trying to write this program without using Counter.Write a Python program to combine values in python list of dictionaries. Go to the editor Sample data:

[{'item': 'item1', 'amount': 400}, {'item': 'item2', 'amount': 300}, {'item': 'item1', 'amount': 750}]
**Expected Output: {'item1': 1150, 'item2': 300}**

So far here's my code.

a=[{'item': 'item1', 'amount': 400}, {'item': 'item2', 'amount': 300}, {'item': 'item1', 'amount': 750}]    
cp={}
val=0
for d in a:
    if d['item'] not in cp:
        cp[d['item']]=d['amount']
print(cp)   

My output: {'item1': 400, 'item2': 300}

How can I combined the total of of 'item1'?Any help is appreciated?

Answer 1

a=[{'item': 'item1', 'amount': 400}, {'item': 'item2', 'amount': 300}, {'item': 'item1', 'amount': 750}]    
cp={}
val=0
for d in a:
    if d['item'] not in cp:
        cp[d['item']] = d['amount']
    else:
        cp[d['item']] += d['amount'] 
print(cp) 

Answer 2

Here is one way:

from collections import defaultdict

lst = [{'item': 'item1', 'amount': 400},
       {'item': 'item2', 'amount': 300},
       {'item': 'item1', 'amount': 750}]

d = defaultdict(int)

for i in lst:
    d[i['item']] += i['amount']

# defaultdict(<class 'int'>, {'item1': 1150, 'item2': 300})

Answer 3

d = {}
for a_dict in all_my_dicts:
    for key in a_dict:
       d[key] = d.get(key,0)+a_dict[key]

I guess maybe

Answer 4

You can use defaultdict here.

from collections import defaultdict
for d in l:
    data[d['item']] += d['amount']

Out[72]: defaultdict(int, {'item1': 1150, 'item2': 300})