python - CSV Reader 对象获取 ValueError : I/O operation on closed file?

Question

我正在创建一个 csv.reader 对象，并将其设置为实例变量，但是当我尝试迭代它时，出现错误，提示我正在尝试在封闭的对象上进行操作文件。 reader 是否仍然以某种方式链接到该文件？我将其分配在我的 with open(blah) block 中，所以我很困惑为什么会发生这种情况。

这是我的代码:

    def __init__(self, infile, header_file, transact_file):
        self.infile = infile
        self.header_of = header_file
        self.transact_of = transact_file

    def create_reader(self):
        """Create a csv reader."""

        with open(self.infile, 'r') as inf:
            logging.info('Infile name: {0}'.format(inf))
            self.csv_reader = reader(inf, quotechar='"')

    def parse_headers(self):
        """Separate header files ("H", "S") from transaction files."""

        headers = []
        transactions = []

        for row in self.csv_reader:
            row_type = row[0]
            logging.info('Row type is: {0}'.format(row_type))
            if row_type == 'H':
                logging.info('Row added to header list.')
                headers.append(row)
            elif row_type == 'S':
                if row not in headers:
                    logging.info('Row added to header list.')
                    headers.append(row)
            else:
                logging.info('Row added to transaction list.')
                transactions.append(row)

        # Debugging and verification
        logging.info('Header list contains: {0}'.format('\n'.join([str(header) for header
            in headers])))
        logging.info('Transaction list contains: {0}'.format(
            '\n'.join([str(trans) for trans in transactions])))

这是我的错误堆栈:

Traceback (most recent call last):                                                                                    x
  File "./gen_pre.py", line 155, in <module>                                                                          x
    main()                                                                                                            x
  File "./gen_pre.py", line 25, in main                                                                               x
    parser.run_process()                                                                                              x
  File "./gen_pre.py", line 140, in run_process                                                                       x
    self.parse_headers()                                                                                              x
  File "./gen_pre.py", line 68, in parse_headers                                                                      x
    for row in self.csv_reader:                                                                                       x
ValueError: I/O operation on closed file  

Answer 1

当您离开区 block 时，

with 会自动关闭文件。

你必须做

self.inf = open(self.infile, 'r')

self.csv_reader = reader(self.inf, quotechar='"') # self.inf

您必须手动关闭该文件。

def close_reader(self):
    self.csv_reader.close()
    self.inf.close()