Pythonitertools.groupby多值

Question

我从数据库返回的记录如下：

region       month_taken         total_att num_classes
Colorado    2013-01-01 00:00:00.000 78485   4648
Colorado    2013-02-01 00:00:00.000 71769   4162
Midwest     2013-01-01 00:00:00.000 110508  7101
Midwest     2013-02-01 00:00:00.000 103545  6410

我正试图把他们列入名单：

总资产：

^{pr2}$

num_类：

[{"data": [4648, 4162], "name": "Colorado"}, {"data": [7101, 6410], "name": "Midwest"}]

我发现了itertools.groupby这是我想要的，但是我很难用一个以上的值列表（因为没有更好的术语）。在

totalResults = []            
for key, location in groupby(rows, lambda k: k[0]):
    totalRow = dict()
    totalRow['name'] = key
    totalRow['data'] = [x[2] for x in location]
    totalResults.append(totalRow)

太好了，这让我得到了我的全部附件列表，但是我做了一个额外的groupby循环来创建“num_classes”列表，这看起来很可笑。我在文档中看到了这一点，但老实说，如果我将其转换为列表，我不太确定这意味着什么，也不知道如何处理我的问题：

The returned group is itself an iterator that shares the underlying iterable with groupby(). Because the source is shared, when the groupby() object is advanced, the previous group is no longer visible. So, if that data is needed later, it should be stored as a list:

那么，如何在groupby（rows，lambda k:k[0]）中创建列表而不必为key，location执行multiple操作呢？在

我希望这是清楚的，但很高兴提供更多的必要信息。在

Answer 1

totalResults = [] 
totalClasses = []           
for key, location in groupby(rows, lambda k: k[0]):
    location = list(location)
    totalResults.append(dict(name=key, data=[x[2] for x in location]))
    totalClasses.append(dict(name=key, data=[x[3] for x in location]))