python - U模式和w+模式下如何写文件？

Question

我希望我的代码在MacOS和Windows下都能正常写入文本，所以我希望这个脚本具有模式U的功能，同时具有w+的功能。

我应该如何处理 file.open() 中的模式参数？

Answer 1

不支持以通用换行模式写入。来自 the PEP :

There is no special support for output to file with a different newline convention, and so mode "wU" is also illegal.

和

There is no output implementation of universal newlines, Python programs are expected to handle this by themselves or write files with platform-local convention otherwise. The reason for this is that input is the difficult case, outputting different newlines to a file is already easy enough in Python.

这实际上是通过尝试 Uw+ 时返回的错误来暗示的:

ValueError: universal newline mode can only be used with modes starting with 'r'

请注意，Ur+ 不会失败，但它也不会对写入进行任何替换；我可以在 Mac 上执行 f.write('test\r\n')(OS X 使用 Unix 换行符)，并且 Windows 换行符会出现在我的文件中。

编辑:看来Python actually offers platform-specific newline output by default anyway ，只要您将 b 关闭即可。

...The default is to use text mode, which may convert '\n' characters to a platform-specific representation on writing and back on reading.