[Python-ideas] Parenthesized Compound With Statement

[Andrew Barnert]

First, you can always do this:

    with open("/long/path/to/file1") as file1, open(
        "/long/path/to/file2") as file2:

Not exactly beautiful, but perfectly legal and PEP-8-compliant.

Or, of course:

    with open("/long/path/to/file1") as file1:
        with open("/long/path/to/file2") as file2:

But the best solution is probably:

    path1 = "/long/path/to/file1"
    path2 = "/long/path/to/file2"
    with open(path1) as file1, open(path2) as file2:

Meanwhile, PEP 8 doesn't say never to use backslashes no matter what. While it says parens "should be used in preference to using a backslash for line continuation", it also says, "But most importantly: know when to be inconsistent -- sometimes the style guide just doesn't apply. When in doubt, use your best judgment." In particular, it specifically says that "When applying the rule would make the code less readable, even for someone who is used to reading code that follows the rules", you should break it.

So you've got four options in today's language. Is it worth changing the syntax to add a fifth?

On Tue, Jul 2, 2013 at 3:37 PM, Matthew Lefavor <mclefavor at gmail.com> wrote:
>> As you all know, Python supports a compound "with" statement to avoid the
>> necessity of nesting these statements.
>> 
>> Unfortunately, I find that using this feature often leads to exceeding the
>> 79-character recommendation set forward by PEP 8.
>> 
>> # The following is over 79 characters
>> with open("/long/path/to/file1") as file1, open("/long/path/to/file2") as
>> file2:
>>    pass
>> 
>> This can be avoided by using the line continuation character, like so:
>> 
>> with open("/long/path/to/file1") as file1, \
>>        open("/long/path/to/file2") as file2:
>>    pass
>> 
>> But PEP-8 prefers using implicit continuation with parentheses over line
>> continuation. PEP 328 states that using the line continuation character is
>> "unpalatable", which was the justification for allowing multi-line imports
>> using parentheses:
>> 
>> from package.subpackage import (UsefulClass1, UsefulClass2,
>>                                ModuleVariable1, ModuleVariable2)
>> 
>> Is there a reason we cannot do the same thing with compound with statements?
>> Has this been suggested before? If so, why was it rejected?
>> 
>> with (open("/long/path/to/file1") as file1,
>>      open("/long/path/to/file2") as file2):
>>    pass
>> 
>> I would be happy to write the PEP for this and get plugged in to the Python
>> development process if this is an idea worth pursuing.
>> 
>> ML
>> 
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