Python多行with语句

Question

with在python中创建多行的干净方法是什么？我想在一个内打开多个文件with，但它足够靠右，足以在多行上显示。像这样：

class Dummy:
    def __enter__(self): pass
    def __exit__(self, type, value, traceback): pass

with Dummy() as a, Dummy() as b,
     Dummy() as c:
    pass

不幸的是，这是一个SyntaxError。所以我尝试了这个：

with (Dummy() as a, Dummy() as b,
      Dummy() as c):
    pass

也是语法错误。但是，这可行：

with Dummy() as a, Dummy() as b,\
     Dummy() as c:
    pass

但是，如果我想发表评论怎么办？这不起作用：

with Dummy() as a, Dummy() as b,\
     # my comment explaining why I wanted Dummy() as c\
     Dummy() as c:
    pass

\s的位置也没有任何明显的变化。

有没有一种干净的方法来创建with允许多行注释的多行语句？

Answer 1

这在Python 3.9中已修复！

https://github.com/we-like-parsers/pegen/issues/229

with (Dummy() as a,
        Dummy() as b,
        # my comment explaining why I wanted Dummy() as c
        Dummy() as c):
    pass

这证明它有效：

Python 3.9.0a6 (default, Jun 20 2020, 14:52:53) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.15.0 -- An enhanced Interactive Python. Type '?' for help.

In [3]: with (open('x') 
   ...:        as f): 
   ...:     pass 
   ...:                                                                                                                                                                                                 
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-3-47d5a51db08b> in <module>
----> 1 with (open('x')
      2        as f):
      3     pass
      4

FileNotFoundError: [Errno 2] No such file or directory: 'x'

In [4]:                                                                                                                                                                                                 
Do you really want to exit ([y]/n)? y

wPython 3.8.2 (default, May  8 2020, 20:08:31) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.15.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: with (open('x') 
   ...:       as f): 
   ...:     pass                                                                                                                                                                                        
  File "<ipython-input-1-e538abd13934>", line 2
    as f):
    ^
SyntaxError: invalid syntax