Question

如何转换Python＆＃39;无＆＃39;输入＆＃39; NULL＆＃39;类型？我使用python-vertica模块查询Vertica数据库，并将结果集写入CSV文件，其中Python CSV模块将NULL作为None插入。因此，当我将此CSV文件导入Vetica数据库时，我将获得空字符串作为＆＃39; ＆＃39;在哪里我希望它是NULL。我猜这里的问题是因为Python无类型。我该如何解决这个问题？

以下是将数据导出为CSV的代码：

def get_data(table, startDate, endDate, config):
  connFrom = vertica_connect_from(config)
  cursor = connFrom.cursor()

  if startDate == endDate:
      command = "select * from dev.{} where report_date='{}'".format(table,startDate)
  else:
      command = "select * from dev.{} where report_date between '{}' and '{}'".format(table, startDate, endDate)

  cursor.execute(command)
  rows = cursor.fetchall()

  with open(filePath, 'w') as csvfile:
      writer = csv.writer(csvfile, delimiter="|")
      for row in rows:
          for index, item in enumerate(row):
              if (item == 0.0):
                  row[index] = 0
          writer.writerow(row)
      logger.info('Data has been copied and written to CSV file at %s', filePath)

  connFrom.close()

以下是我导入它的方式：

def load_data(table, config):
  connTo = vertica_connect_to(config)
  cur = connTo.cursor()

  importCommand = "copy qa.{} from stdin null as '' rejected data '{}' exceptions '{}'".format(table,rejectedLog, exceptionLog)
  with open(filePath, 'r') as fil:
      try:
          cur.copy(importCommand, fil)
      except Exception as e:
          logger.error('%s', e)
      logger.info('Data has been copied, check rejected/exception files at /tmp on the destination host for any errors')

  connTo.close()

Answer 1

如果这里的问题是你想使用NULL作为代币，只需添加一个像0.0一样的替换。

if not item: 
    row[index] = 'NULL'

然后更改您的副本以适应。

null as 'NULL'

如何转换Python＆＃39;无＆＃39;输入＆＃39; NULL＆＃39;类型

1 个答案: