将 Python 字符串列表作为字符串中的动态变量传递

Question

我不明白为什么这不起作用。我试图将字符串列表作为用作数据库查询的字符串内循环的一部分传递。这是我收到的错误：

\porfiler03.ar.local\gtdshare\vortex\monthly_variability\scripts\wind_index_chinook_region_3plots_working_monthly.py:71 in get_db_data
    crs_obj.execute(query)

UndefinedColumn: column "east" does not exist
LINE 5: ...s_name = 'UNITED STATES'  AND maint_region_name = EAST  AND ...

这是代码：

regions = ['EAST','CENTRAL']

for x in regions:
    randall_query = f"""select plant_mos_adj_wind.plant_name, plant_mos_adj_wind.business_name,plant_mos_adj_wind.business_code,plant_mos_adj_wind.wind_speed_ms,
    plant_mos_adj_wind.maint_region_name, plant_mos_adj_wind.wind_direction_deg, plant_mos_adj_wind.mos_time, plant_mos_adj_wind.total_current_capacity,
    plant_mos_adj_wind.dataset
    from vortex.plant_mos_adj_wind
    where business_name = 'UNITED STATES'  AND maint_region_name = {x}  AND dataset = 'ERA5'"""
    try:
       connection = psycopg2.connect(user="cms_app",
                                      password="xxxxx",
                                      host="frupaapg02.ar.local",
                                      port="xxxx",
                                      database="xxxx")
       print("Selecting rows from vortex plant_mos_adj_wind table using cursor.fetchmany")
       cursor = connection.cursor()
       cdata = get_db_data(cursor, randall_query, False, True).round(1) #panda df
       postgreSQL_select_Query = f"""select plant_name, business_name, maint_region_name, total_current_capacity, mos_time, wind_speed_ms, wind_direction_deg, dataset
       from vortex.plant_mos_adj_wind
       where business_name = 'UNITED STATES' AND maint_region_name = {x}  AND dataset = 'ERA5'"""
    
       cursor.execute(postgreSQL_select_Query)
       chinookmos_records = cursor.fetchall()
    finally:
        #closing database connection.
        if(connection):
            cursor.close()
            connection.close()
            print("PostgreSQL connection is closed")
    
    #iterate the columns
            print("Column headers for cdata are:")
            for col in cdata.columns:
                print(col)

这应该使用 f 字符串函数并替换区域中的 x 来工作，但是您可以看到它由于 EAST 参数而失败，并且显然应该是“EAST”传递，因为我的想法是字符串。

Answer 1

我推荐2个解决方案：

1. 在第一个查询行之后删除查询行中 for 循环的选项卡

    randall_query = f"""select plant_mos_adj_wind.plant_name, plant_mos_adj_wind.business_name,plant_mos_adj_wind.business_code,plant_mos_adj_wind.wind_speed_ms, plant_mos_adj_wind.maint_region_name, plant_mos_adj_wind.wind_direction_deg, plant_mos_adj_wind.mos_time, plant_mos_adj_wind.total_current_capacity, plant_mos_adj_wind.dataset from vortex.plant_mos_adj_wind where business_name = 'UNITED STATES'  AND maint_region_name = {x}  AND dataset = 'ERA5'"""

2. 检查数据库中是否存在列名EAST。

Answer 2

f string 只是将变量的值放入字符串中，因此您需要在 {x} 中添加单引号（''）。

转换这个 AND maint_region_name = {x}

对此： AND maint_region_name = '{x}'