python - 使用函数打开文件(类型为 BytesIO)

Question

我有以下代码:

这部分在内存中生成 CSV:

def to_csv(events: list) -> io.BytesIO():
    if not events:
        return None
    bio = io.BytesIO()
    iow = io.TextIOWrapper(bio)
    writer = csv.DictWriter(iow, fieldnames=events[0].keys())
    writer.writeheader()
    writer.writerows(events)
    iow.flush()
    bio.seek(0)
    return bio

此部分将此文件发送到 FTP 服务器:

def send_data(self, bytes: io.BytesIO) -> str:
    filename = f"{time.time()}.csv"
    if not bytes:
        self.__logger.warning("No data to send")
        return None
    try:
        self.__ftp.storbinary(f"STOR {filename}", bytes)
    except ftp.all_errors as e:
        self.__logger.error(
            "FTP fail data send",
            extra={
                "host": self.__cfg.ftp.host,
                "type": type(e).__name__,
                "line": e.__traceback__.tb_lineno,
                "file": __file__,
                "detail": e,
            },
        )
        return None

传递给 send_data 的文件已关闭。我该如何重新打开它？ 我试图做这样的事情:

f = open(bytes, "rb")
print(f.getvalue())

但是返回错误:

expected str, bytes or os.PathLike object, not _io.BytesIO

回溯:

Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/operators/python.py", line 171, in execute
    return_value = self.execute_callable()
  File "/home/airflow/.local/lib/python3.7/site-packages/airflow/operators/python.py", line 189, in execute_callable
    return self.python_callable(*self.op_args, **self.op_kwargs)
  File "/opt/airflow/dags/accounting/main.py", line 29, in process_events
    result = Uploader(logger, cfg).send_data(csv_file)
  File "/opt/airflow/dags/accounting/packages/uploader.py", line 57, in send_data
    self.__ftp.storbinary(f"STOR {filename}", bytes)
  File "/usr/local/lib/python3.7/ftplib.py", line 513, in storbinary
    buf = fp.read(blocksize)
ValueError: I/O operation on closed file.

Answer 1

一旦 to_csv 使用 io.TextIOWrapper 完成，它需要从底层 io.BytesIO 对象分离包装器，以停止试图关闭 BytesIO 对象的包装器:

iow.detach()