python - 如何在 python 字典列表中组合值

Question

我有一个看起来像这样的字典列表:

l = [{'name': 'john', 'amount': 50}, {'name': 'al', 'amount': 20}, {'name': 'john', 'amount': 80}]

有什么方法可以合并/合并匹配的名称值字典并求和吗？

Answer 1

您可以使用 collections.Counter() object将名称映射到数量，并在进行时对它们求和:

from collections import Counter

summed = Counter()
for d in l:
    summed[d['name']] += d['amount']
result = [{'name': name, 'amount': amount} for name, amount in summed.most_common()]

然后结果也按金额排序(最高在前):

>>> from collections import Counter
>>> l = [{'name': 'john', 'amount': 50}, {'name': 'al', 'amount': 20}, {'name': 'john', 'amount': 80}]
>>> summed = Counter()
>>> for d in l:
...     summed[d['name']] += d['amount']
... 
>>> summed
Counter({'john': 130, 'al': 20})
>>> [{'name': name, 'amount': amount} for name, amount in summed.most_common()]
[{'amount': 130, 'name': 'john'}, {'amount': 20, 'name': 'al'}]