text: import pymysql
  
  def connect_sql():
      conn = pymysql.connect(host='localhost', user='root', password='xn410a', db='zyt_spiders', charset='utf8')
      return conn
  
  def delete_old_items(conn, table_name, time):
      cursor = conn.cursor()
      sql = 'delete from {} where record_time < "{}";'.format(table_name, time)
      #print(sql)
      cursor.execute(sql)
      sql_optimize = 'optimize table {}'.format(table_name)
      cursor.execute(sql_optimize)
  
  
  if __name__ == "__main__":
      conn = connect_sql()
  
      table_name_list = ["caiyun_15d_weather",
                         "caiyun_48h_weather",
                         "caiyun_real_weather",
                         "heweather_3d",
                         "heweather_real",
                         "nmc_2d_weather",
                         "nmc_real_weather",
                         "openweather_5d",
                         "openweather_real",
                         "seniverse_15d_weather",
                         "seniverse_real_weather"]
      for table_name in table_name_list:
          delete_old_items(conn=conn, table_name=table_name, time="2019-11-18 00:00:00")
          print(table_name + " is cleaned.")
  