在一个循环中求和多个值

Question

这就是我想要的：

cr.execute(#some query)    
lines = self.cr.dictfetchall()
total_qty = 0.00
total_weight = 0.00
total_weight_net = 0.00
total_volume = 0.00
for line in lines:
    total_qty += line['product_qty']
    total_weight += line['weight']
    total_volume += line['volume']

有没有更好的方法来做这种总结？谢谢

Answer 1

您可能正在尝试寻找替代循环方法：

lines = [{"a": 10, "b":22},
        {"a": 11, "b":22},
        {"a": 12, "b":20},
        {"a": 15, "b":15},
        {"a": 15, "b":12}]

sumA = sum(itm["a"] for itm in lines)
sumB = sum(itm["b"] for itm in lines)
print sumA
print sumB

打印

63
91

无论如何，正如@MartijnPieters建议的那样，通过sql查询获得总和很可能会更快。