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Re: Python and PEP8 - Recommendations on breaking up long lines?

From Ned Batchelder <ned@nedbatchelder.com>
Subject Re: Python and PEP8 - Recommendations on breaking up long lines?
Date 2013-11-27 22:05 -0500
References <a98cfbef-bc48-41e8-98de-e616f201ffbe@googlegroups.com> <34479463-b8a8-4417-9989-cd29369461c2@googlegroups.com>
Newsgroups comp.lang.python
Message-ID <mailman.3342.1385607934.18130.python-list@python.org> (permalink)

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On 11/27/13 9:03 PM, Victor Hooi wrote:
> Hi,
>
> Also, forgot two other examples that are causing me grief:
>
>      cur.executemany("INSERT INTO foobar_foobar_files VALUES (?)",
>                      [[os.path.relpath(filename, foobar_input_folder)] for filename in filenames])
>
> I've already broken it up using the parentheses, not sure what's the tidy way to break it up again to fit under 80? In this case, the 80-character mark is hitting me around the "for filename" towards the end.

     file_values = [
         (os.path.relpath(filename, foobar_input_folder),)
         for filename in filenames
     ]
     cur.executemany(
         "INSERT INTO foobar_foobar_files VALUES (?)",
         file_values
     )

>
> and:
>
>                      if os.path.join(root, file) not in previously_processed_files and os.path.join(root, file)[:-3] not in previously_processed_files:
>
> In this case, the 80-character mark is actually partway through "previously processed files" (the first occurrence)...

     full_file = os.path.join(root, file)
     full_not_in = full_file not in previously_processed_files
     tail_not_in = full_file[:-3] not in previously_processed_files
     if full_not_in and tail_not_in:
         ...

This has the advantage of naming these complex intermediate conditions, 
and giving you natural places to write comments explaining them.  Why 
[:-3] for example?

More, shorter, statements.

--Ned.

>
> Cheers,
> Victor
>

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Thread

Python and PEP8 - Recommendations on breaking up long lines? Victor Hooi <victorhooi@gmail.com> - 2013-11-27 17:57 -0800
  Re: Python and PEP8 - Recommendations on breaking up long lines? Victor Hooi <victorhooi@gmail.com> - 2013-11-27 18:03 -0800
    Re: Python and PEP8 - Recommendations on breaking up long lines? Ben Finney <ben+python@benfinney.id.au> - 2013-11-28 13:55 +1100
    Re: Python and PEP8 - Recommendations on breaking up long lines? Terry Reedy <tjreedy@udel.edu> - 2013-11-27 22:03 -0500
    Re: Python and PEP8 - Recommendations on breaking up long lines? Ned Batchelder <ned@nedbatchelder.com> - 2013-11-27 22:05 -0500
    Re: Python and PEP8 - Recommendations on breaking up long lines? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-11-28 08:12 +0200
      Re: Python and PEP8 - Recommendations on breaking up long lines? Chris Angelico <rosuav@gmail.com> - 2013-11-28 17:22 +1100
    Re: Python and PEP8 - Recommendations on breaking up long lines? Roy Smith <roy@panix.com> - 2013-11-28 10:08 -0500
  Re: Python and PEP8 - Recommendations on breaking up long lines? Ben Finney <ben+python@benfinney.id.au> - 2013-11-28 13:47 +1100
    Re: Python and PEP8 - Recommendations on breaking up long lines? Steven D'Aprano <steve@pearwood.info> - 2013-11-28 03:02 +0000
      Re: Python and PEP8 - Recommendations on breaking up long lines? Ben Finney <ben+python@benfinney.id.au> - 2013-11-28 14:14 +1100
  Re: Python and PEP8 - Recommendations on breaking up long lines? Terry Reedy <tjreedy@udel.edu> - 2013-11-27 21:55 -0500
  Re: Python and PEP8 - Recommendations on breaking up long lines? Ned Batchelder <ned@nedbatchelder.com> - 2013-11-27 21:59 -0500
    Re: Python and PEP8 - Recommendations on breaking up long lines? Steven D'Aprano <steve@pearwood.info> - 2013-11-28 03:58 +0000
      Re: Python and PEP8 - Recommendations on breaking up long lines? Tim Chase <python.list@tim.thechases.com> - 2013-11-28 08:04 -0600
      Re: Python and PEP8 - Recommendations on breaking up long lines? Chris Angelico <rosuav@gmail.com> - 2013-11-29 01:21 +1100
      Re: Python and PEP8 - Recommendations on breaking up long lines? Ned Batchelder <ned@nedbatchelder.com> - 2013-11-28 12:26 -0500
  Re: Python and PEP8 - Recommendations on breaking up long lines? Ben Finney <ben+python@benfinney.id.au> - 2013-11-28 14:06 +1100
  Re: Python and PEP8 - Recommendations on breaking up long lines? Neil Cerutti <mr.cerutti@gmail.com> - 2013-11-27 22:09 -0500
  Re: Python and PEP8 - Recommendations on breaking up long lines? Ethan Furman <ethan@stoneleaf.us> - 2013-11-27 19:15 -0800
  Re: Python and PEP8 - Recommendations on breaking up long lines? Steven D'Aprano <steve@pearwood.info> - 2013-11-28 03:57 +0000
    Re: Python and PEP8 - Recommendations on breaking up long lines? Steven D'Aprano <steve@pearwood.info> - 2013-11-28 04:03 +0000
  Re: Python and PEP8 - Recommendations on breaking up long lines? MRAB <python@mrabarnett.plus.com> - 2013-11-28 12:43 +0000
  Re: Python and PEP8 - Recommendations on breaking up long lines? Walter Hurry <walterhurry@lavabit.com> - 2013-11-28 17:38 +0000
  Re: Python and PEP8 - Recommendations on breaking up long lines? Roel Schroeven <roel@roelschroeven.net> - 2013-11-28 19:37 +0100
  Re: Python and PEP8 - Recommendations on breaking up long lines? Nick Mellor <thebalancepro@gmail.com> - 2013-12-04 17:47 -0800

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