Python:根据多个值+总和合并n个字典

假设我有一个这样的字典列表:

[{'amount': 42140.0, 'name': 'Payment', 'account_id_credit': 385, 'type': u'expense', 'account_id_debit': 476},  
{'amount': 43926.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'payable', 'account_id_debit': 641},  
{'amount': 3800.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476}, 
{'amount': 46330.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476},  
{'amount': 67357.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'payable', 'account_id_debit': 323}, 
{'amount': 26441.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476} ... ] 

我想将字典合并在一起，这样键“金额”将是字典中所有 金额 的总和，其中 account_id_credit 和 account_id_debit 是相同的，但前提是那些的 type 是 expense。其他类型应该保持原样。

最好的方法是什么？

请您参考如下方法:

一种方法是创建一个中间字典，由 (account_id_credit, account_id_debit) 的元组和总金额值组成的元组作为键，然后从中构建聚合字典列表:

ld = [{'amount': 42140.0, 'name': 'Payment', 'account_id_credit': 385, 'type': u'expense', 'account_id_debit': 476},  
{'amount': 43926.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'payable', 'account_id_debit': 641},  
{'amount': 3800.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476}, 
{'amount': 46330.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476},  
{'amount': 67357.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'payable', 'account_id_debit': 323}, 
{'amount': 26441.0, 'name': 'Payment', 'account_id_credit': 695, 'type': u'expense', 'account_id_debit': 476} ] 
 
 
d2 = {} 
for d in ld: 
    if d['type'] != 'expense': 
        continue 
    k = (d['account_id_credit'], d['account_id_debit']) 
    try: 
        d2[k] += d['amount'] 
    except KeyError: 
        d2[k] = d['amount'] 
 
ld2 = [] 
for d in ld: 
    if d['type'] != 'expense': 
        ld2.append(d) 
        continue 
    k = (d['account_id_credit'], d['account_id_debit']) 
    try: 
        d['amount'] = d2[k] 
        # We're done with this amount sum: remove it from the intermediate dict 
        del d2[k] 
    except KeyError: 
        continue 
    ld2.append(d) 
print ld2 
 
[{'account_id_credit': 385, 'account_id_debit': 476, 'amount': 42140.0, 'type': u'expense', 'name': 'Payment'}, 
 {'account_id_credit': 695, 'account_id_debit': 641, 'amount': 43926.0, 'type': u'payable', 'name': 'Payment'}, 
 {'account_id_credit': 695, 'account_id_debit': 476, 'amount': 76571.0, 'type': u'expense', 'name': 'Payment'}, 
 {'account_id_credit': 695, 'account_id_debit': 323, 'amount': 67357.0, 'type': u'payable', 'name': 'Payment'}]