CSV Reader object getting ValueError: I/O operation on closed file?

Question

我正在创建一个 csv.reader 对象，将其设置为一个实例变量，但是当我尝试遍历它时，我收到一条错误消息，提示我正在尝试对一个已关闭的文件进行操作。 reader 是否仍以某种方式链接到文件？我在我的 with open(blah) 块中分配它，所以我很困惑为什么会这样。

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

with 离开块时自动关闭文件。

你必须做

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

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

并且您必须手动关闭该文件。

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

Answer 2

上下文管理器很棒，因为它们会自动为您关闭文件。您可以读取整个文件并将行列表传递给 CSV reader:

，而不是手动打开和关闭文件

def create_reader(self):
    """Create a csv reader."""
    with open(self.infile, 'r') as inf:
        logging.info('Infile name: {0}'.format(inf))
        file_data = inf.readlines()
    self.csv_reader = reader(file_data, quotechar='"')

csv.reader 对象将接受它可以迭代的任何内容，因此文件中每一行的列表（来自 readlines）都可以正常工作。

CSV Reader object getting ValueError: I/O operation on closed file?

CSV Reader object getting ValueError: I/O operation on closed file?

python

python-2.x