使用一个字典(Python)对列表列表的不同元素进行求和

Question

我有一份清单：

    [Racing, 100]
    [Crossi, 100]
    [Racing, 120]
    [Racing, 130]
    [Marcas, 105]
    [Marcas, 109]
    [Crossi, 130]
    [Crossi, 104]

我想要赛车，马尔卡斯和克罗西的总金额。如果可能的话，我想用一本关于python的字典来做。如下所示：

    Brads{"Crossi": 334, "Marcas": 214, "Racing":350}

是否可以只使用一个for循环来完成它？

Answer 1

from collections import defaultdict
list_ = [['Racing', 100],['Crossi', 100],['Racing', 120],['Racing', 130],['Marcas', 105],['Marcas', 109],['Crossi', 130],['Crossi', 104]]
dic = defaultdict(int)
for i in list_:
    dic[i[0]] += i[1]
print(dic)

退出：

defaultdict(<class 'int'>, {'Marcas': 214, 'Crossi': 334, 'Racing': 350})

setdefault默认值：

list_ = [['Racing', 100],['Crossi', 100],['Racing', 120],['Racing', 130],['Marcas', 105],['Marcas', 109],['Crossi', 130],['Crossi', 104]]
d = {}
for k,v in list_:
    d[k] = d.setdefault(k,0) + v
print(d)

退出：

{'Marcas': 214, 'Crossi': 334, 'Racing': 350}

Answer 2

您可以为此使用collections.defaultdict

from collections import defaultdict

l = [['Racing', 100],
     ['Crossi', 100],
     ['Racing', 120],
     ['Racing', 130],
     ['Marcas', 105],
     ['Marcas', 109],
     ['Crossi', 130],
     ['Crossi', 104]]

d = defaultdict(int)
for key, value in l:
    d[key] += value

print(d)输出

defaultdict(<class 'int'>, {'Marcas': 214, 'Racing': 350, 'Crossi': 334})

Answer 3

你可以这样做：

list_of_list = [
    ['Racing', 100],
    ['Crossi', 100],
    ['Racing', 120],
    ['Racing', 130],
    ['Marcas', 105],
    ['Marcas', 109],
    ['Crossi', 130],
    ['Crossi', 104]
]

people = {}

for selected_list in list_of_list:
    name = selected_list[0]
    if name in people:
        people[name] += selected_list[1]
    else:
        people[name] = selected_list[1]