Pandas groupby：仅在部分记录上聚合答案

【问题标题】：Pandas groupby: aggregate only on partial recordsPandas groupby：仅在部分记录上聚合
【发布时间】：2018-09-15 17:50:56
【问题描述】：

我有以下数据框：

id   src     target     duration
001     A      C           4
001     B      C           3
001     C      C           2
002     B      D           5
002     C      D           2

我使用以下代码进行了一些聚合，效果很好。

df_new = df.groupby(['id','target']) \
        .apply(lambda x: pd.Series({'min_duration': min(x['duration']), \
                                    'total_duration':sum(x['duration']), \
                                    'all_src':list(x['src'])
                                   })).reset_index()

现在我只想计算 src != target 记录的总和。我修改了我的代码，如下所示：

df_new = df.groupby(['id','target']) \
        .apply(lambda x: pd.Series({'min_duration': min(x['duration']), \
                                    'total_duration':sum(x['duration']), \
                                    'total_duration_condition':sum(x['duration']) if x['src'] != x['target'], \
                                    'all_src':list(x['src'])
                                   })).reset_index()

然后在我的新行中出现Invalid Syntax 错误：

'total_duration_condition':sum(x['duration']) if x['src'] != x['target']

我想知道仅对部分记录进行求和的正确方法应该是什么？谢谢！

【问题讨论】：

标签： python-3.x pandas aggregate pandas-groupby

【解决方案1】：

尝试编写如下代码

df.groupby(['id','target']).apply(lambda x: pd.Series({'min_duration': min(x['duration']), \
                                    'total_duration':sum(x['duration']), \
                                    'total_duration_condition':sum(x['duration'][x['src'] != x['target']]), \# I change this part
                                    'all_src':list(x['src'])
                                   })).reset_index()

换行

'total_duration_condition':sum(x['duration']) if x['src'] != x['target']

到

sum(x['duration'][x['src'] != x['target']])

【讨论】：