如何在python中使用tempfile.NamedTemporaryFile()

Question

我想用它tempfile.NamedTemporaryFile()来写一些内容然后打开那个文件.我写了以下代码:

tf = tempfile.NamedTemporaryFile()
tfName = tf.name
tf.seek(0)
tf.write(contents)
tf.flush()

但我无法打开此文件,并在记事本或类似的应用程序中查看其内容.有没有办法实现这个目标？为什么我不能这样做:

os.system('start notepad.exe ' + tfName)

在末尾

Answer 1

这可能是以下两个原因之一:

首先,默认情况下,临时文件一关闭就会被删除.要解决此问题:

tf = tempfile.NamedTemporaryFile(delete=False)

然后在其他应用程序中完成查看后手动删除该文件.

或者,它可能是因为文件仍然在Python中打开Windows不允许您使用其他应用程序打开它.

Answer 2

您还可以将其与上下文管理器一起使用,以便在文件超出范围时关闭/删除该文件.如果上下文管理器中的代码引发,它也将被清除.

import tempfile
with tempfile.NamedTemporaryFile() as temp:
    temp.write('Some data')
    temp.flush()

    # do something interesting with temp before it is destroyed

Answer 3

这是一个有用的上下文管理器。（在我看来，这个功能应该是 Python 标准库的一部分。）

# python2 or python3
import contextlib
import os

@contextlib.contextmanager
def temporary_filename(suffix=None):
  """Context that introduces a temporary file.

  Creates a temporary file, yields its name, and upon context exit, deletes it.
  (In contrast, tempfile.NamedTemporaryFile() provides a 'file' object and
  deletes the file as soon as that file object is closed, so the temporary file
  cannot be safely re-opened by another library or process.)

  Args:
    suffix: desired filename extension (e.g. '.mp4').

  Yields:
    The name of the temporary file.
  """
  import tempfile
  try:
    f = tempfile.NamedTemporaryFile(suffix=suffix, delete=False)
    tmp_name = f.name
    f.close()
    yield tmp_name
  finally:
    os.unlink(tmp_name)

# Example:
with temporary_filename() as filename:
  os.system('echo Hello >' + filename)
  assert 6 <= os.path.getsize(filename) <= 8  # depending on text EOL
assert not os.path.exists(filename)