python - 进行多条件求和的循环

Question

我有一个以下形式的数据框:

df = [["john","2019","30.2"] , ["john","2019","40"] , ["john","2020","50.3"] , 
      ["amy","2019","60"] , ["amy","2019","20"] , ["amy","2020","40.1"]]

我想要的结果是最后一个索引的多条件求和列表，而前两个索引相等:

> [["john", "2019", "70.2"] ,  ["john","2020","50.3"] , ["amy","2019","80"] , ["amy","2020","40.1"]]

我尝试做的是一个 for 循环，检查每个条件的相等性，然后在条件成立时对最后一个索引求和 - 这是某种伪代码:

for i in df[i]:
   if df[i][0] == df[i+1][0] and df[i][1] == df[i+1][1]: #if both conditions are true
      sum1 = sum(float(df[i][2]))
      lst = []
      lst.append(df[i][0])
      lst.append(df[i][1])
      lst.append(str(sum1))

编辑:希望有一个不使用包的解决方案。

Answer 1

以下代码不使用任何包。从 Python 3.7 开始，所有字典都是 insertion-ordered ，这个事实在下面的代码中使用，以便最终结果具有元素原始外观的顺序。如果由于某种原因您的 python 低于 3.7，请告诉我，我将修改代码以显式进行排序，而不是依赖此语言功能。

Try it online!

df = [["john","2019","30.2"], ["john","2019","40"], ["john","2020","50.3"],
      ["amy","2019","60"], ["amy","2019","20"], ["amy","2020","40.1"]]

r = {}
for *a, b in df:
    a = tuple(a)
    if a not in r:
       r[a] = 0
    r[a] += float(b)
r = [list(k) + [str(v)] for k, v in r.items()]

print(r)

输出:

[['john', '2019', '70.2'], ['john', '2020', '50.3'], ['amy', '2019', '80.0'], ['amy', '2020', '40.1']]