[Python-ideas] with statement syntax forces ugly line breaks?

[M.-A. Lemburg]

Mark Summerfield wrote:
> Hi,
> 
> I can't see a _nice_ way of splitting a with statement over mulitple
> lines:
> 
> class FakeContext:
>     def __init__(self, name):
>         self.name = name
>     def __enter__(self):
>         print("enter", self.name)
>     def __exit__(self, *args):
>         print("exit", self.name)
> 
> with FakeContext("a") as a, FakeContext("b") as b:
>     pass # works fine
> 
> 
> with FakeContext("a") as a,
>      FakeContext("b") as b:
>     pass # synax error
> 
> 
> with (FakeContext("a") as a,
>       FakeContext("b") as b):
>     pass # synax error
> 
> The use case where this mattered to me was this:
> 
>     with open(args.actual, encoding="utf-8") as afh,
>     open(args.expected, encoding="utf-8") as efh: actual =
>     [line.rstrip("\n\r") for line in afh.readlines()] expected =
>     [line.rstrip("\n\r") for line in efh.readlines()]
> 
> Naturally, I could split the line in an ugly place:
> 
>     with open(args.actual, encoding="utf-8") as afh, open(args.expected,
> 	    encoding="utf-8") as efh:
> 
> but it seems a shame to do so. Or am I missing something?

Why do you need to put everything on one line ?

afh = open(args.actual, encoding="utf-8")
efh = open(args.expected, encoding="utf-8")

with afh, efh:
   ...

In the context of files, the only purpose of the with statement
is to close them when leaving the block.

>>> a = open('/etc/passwd')
>>> b = open('/etc/group')
>>> with a,b: print a.readline(), b.readline()
...
at:x:25:25:Batch jobs daemon:/var/spool/atjobs:/bin/bash
at:!:25:

>>> a
<closed file '/etc/passwd', mode 'r' at 0x7f0093e62390>
>>> b
<closed file '/etc/group', mode 'r' at 0x7f0093e62420>

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Marc-Andre Lemburg
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