如何使用“with open"打开多个文件?在 Python 中? [英] How can I open multiple files using "with open" in Python?

问题描述

我想一次更改几个文件，如果我可以写入所有文件.我想知道我是否可以将多个 open 调用与 with 语句结合起来:

I want to change a couple of files at one time, iff I can write to all of them. I'm wondering if I somehow can combine the multiple open calls with the with statement:

try:
  with open('a', 'w') as a and open('b', 'w') as b:
    do_something()
except IOError as e:
  print 'Operation failed: %s' % e.strerror

如果这是不可能的，那么这个问题的优雅解决方案会是什么样的?

If that's not possible, what would an elegant solution to this problem look like?

推荐答案

从 Python 2.7(或分别为 3.1)开始，您可以编写

As of Python 2.7 (or 3.1 respectively) you can write

with open('a', 'w') as a, open('b', 'w') as b:
    do_something()

在早期版本的 Python 中，有时可以使用contextlib.nested() 嵌套上下文经理.但是，这在打开多个文件时不会按预期工作——有关详细信息，请参阅链接的文档.

In earlier versions of Python, you can sometimes use contextlib.nested() to nest context managers. This won't work as expected for opening multiples files, though -- see the linked documentation for details.

在极少数情况下，您想同时打开可变数量的文件，您可以使用 contextlib.ExitStack，从 Python 3.3 版开始:

In the rare case that you want to open a variable number of files all at the same time, you can use contextlib.ExitStack, starting from Python version 3.3:

with ExitStack() as stack:
    files = [stack.enter_context(open(fname)) for fname in filenames]
    # Do something with "files"

大多数情况下，您有一组可变的文件，但您可能希望一个接一个地打开它们.

Most of the time you have a variable set of files, you likely want to open them one after the other, though.

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