python - 如何根据另一列对一行中的特定列求和？

Question

你能帮我解决以下问题吗：

示例文件：

我尝试从每行的特定开始日期开始汇总 6 个月的总和。

总和应显示在新列中（从 startdate 算起 6 个月的总和）

我的第一个想法是使用以下代码获取它：

df['sum_6_months'] = df.loc[:,'01.2018':'06.2018'].apply(sum, axis=1)

但此代码不是单独的，仅适用于所有行中的时间范围 (01.18-06.18)。

df = pd.DataFrame(np.array([[1, 5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4,1], [1, 5, 3, 4, 5, 6, 7, 7,8,2,5,7,3,4,2],[1,5,3, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4],
                             [1, 5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4,3], [1, 5, 3, 4, 5, 6, 7, 7,8,2,5,7,3,4,4],[1,5,5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4],
                             [1, 5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4,5], [1, 5, 3, 4, 5, 6, 7, 7,8,2,5,7,3,4,5],[1,5,2, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4],
                             [1, 5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4,6], [1, 5, 3, 4, 5, 6, 7, 7,8,2,5,7,3,4,2],[1,5,5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4],
                             [1, 5, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4,4], [1, 5, 3, 4, 5, 6, 7, 7,8,2,5,7,3,4,2],[1,5,1, 3, 4, 5, 6, 7, 7, 8,2,5,7,3,4]]),
                   columns=['01.2018', '02.2018', '03.2018', '04.2018', '05.2018','06.2018', '07.2018', '08.2018',
                            '09.2018','10.2018', '11.2018', '12.2018','01.2019', '02.2019', '03.2019'])

date = [01.2018, 03.2018,04.2018,05.2018,03.2018,01.2018, 03.2018,04.2018,05.2018,03.2018,01.2018, 03.2018,04.2018,05.2018,03.2018]
df['Startdate']= date

标签： pythonaggregatemultiple-columnsrows

Answer 1

df['Startdate']=df['Startdate'].astype(str).str.rjust(7,'0')

df_columns = df.columns.tolist()
def get_sum_six(df_list):
    start_date_index = df_columns.index(df_list[-1])
    df_list = df_list[0:-1]
    sum_of_six = sum(df_list[start_date_index: start_date_index + min(len(df_list)-start_date_index, 6)])
    return (sum_of_six)

df['sum_last_six'] = df.apply(lambda x: get_sum_six(x.tolist()), axis=1)