Python and PEP8 - Recommendations on breaking up long lines?

Newsgroups	comp.lang.python
Date	2013-11-27 17:57 -0800
Message-ID	<a98cfbef-bc48-41e8-98de-e616f201ffbe@googlegroups.com> (permalink)
Subject	Python and PEP8 - Recommendations on breaking up long lines?
From	Victor Hooi <victorhooi@gmail.com>

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Hi,

I'm running pep8 across my code, and getting warnings about my long lines (> 80 characters).

I'm wonder what's the recommended way to handle the below cases, and fit under 80 characters.

First example - multiple context handlers:

with open(self.full_path, 'r') as input, open(self.output_csv, 'ab') as output:

and in my case, with indents, the 80-character marks is just before the ending "as output".

What's the standard recognised way to split this across multiple lines, so that I'm under 80 characters?

I can't just split after the "as input," as that isn't valid syntax, and there's no convenient parentheses for me to split over.

Is there a standard Pythonic way?

Second example - long error messages:

self.logger.error('Unable to open input or output file - %s. Please check you have sufficient permissions and the file and parent directory exist.' % e)

I can use triple quotes:

self.logger.error(
"""Unable to open input or output file - %s. Please check you
have sufficient permissions and the file and parent directory
exist.""" % e)

However, that will introduce newlines in the message, which I don't want.

I can use backslashes:

self.logger.error(
'Unable to open input or output file - %s. Please check you\
have sufficient permissions and the file and parent directory\
exist.' % e)

which won't introduce newlines.

Or I can put them all as separate strings, and trust Python to glue them together:

self.logger.error(
'Unable to open input or output file - %s. Please check you'
'have sufficient permissions and the file and parent directory'
'exist.' % e)

Which way is the recommended Pythonic way?

Third example - long comments:

""" NB - We can't use Psycopg2's parametised statements here, as
that automatically wraps everything in single quotes.
So s3://my_bucket/my_file.csv.gz would become s3://'my_bucket'/'my_file.csv.gz'.
Hence, we use Python's normal string formating - this could
potentially exposes us to SQL injection attacks via the config.yaml
file.
I'm not aware of any easy ways around this currently though - I'm
open to suggestions though.
See
http://stackoverflow.com/questions/9354392/psycopg2-cursor-execute-with-sql-query-parameter-causes-syntax-error
for further information. """

In this case, I'm guessing a using triple quotes (""") is a better idea with multi-line comments, right?

However, I've noticed that I can't seem to put in line-breaks inside the comment without triggering a warning. For example, trying to put in another empty line in between lines 6 and 7 above causes a warning.

Also, how would I split up the long URLs? Breaking it up makes it annoying to use the URL. Thoughts?

Cheers,
Victor

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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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