python - 如何在不排序的情况下迭代组？

Question

我有一个像这样仔细排序的数据框:

x = pd.DataFrame({'col1':['b', 'e','e', 'g','g', 'f','f'],
                  'col2':['f', 'g','f', 'f','e', 'g','e'],
                  'col3':[ 1 ,  7 , 2 ,  6 , 7 ,  20, 5 ]})

我想将各组汇总为每行一行，保留顺序

names, totals, fs = zip(* list( (name, total(group), f(group)) for name, group in x.groupby('col1'))  )

out =   pd.DataFrame({'lang':names,
                      'total':totals,
                      'partners':tails})

但是在 out行按 col1 排序。而x.groupby('col1').heads()以正确的顺序生成所有内容，如 [name for name, _ in x.groupby('col1')] 所示进行迭代返回['b', 'e', 'f', 'g']何时“f”应位于“g”后面

如何在不排序的情况下循环遍历组？

Answer 1

正如评论中所讨论的，您所需要的只是

groupby("col1", sort=False)

取自 the documentation :

sort : boolean, default True

Sort group keys. Get better performance by turning this off. Note this does not influence the order of observations within each group. groupby preserves the order of rows within each group.