[Python-ideas] Implicit string literal concatenation considered harmful?

[Barry Warsaw]

On May 10, 2013, at 09:28 PM, M.-A. Lemburg wrote:

>>> Would it be reasonable to start deprecating this and eventually remove
>>> it from the language?

I'm pretty mixed.  OT1H, you're right, it's a common mistake and often *very*
hard to spot.  A SyntaxWarning when it appears on a single line doesn't help
because I'm much more likely to forget a trailing comma in situations like:

files = [
    '/tmp/foo',
    '/etc/passwd'
    '/etc/group',
    '/var/cache',
    ]

(g'wan, spot the missing comma ;).

OTOH, doing things like:

>s = ('abc\n'
>     'def\n'
>     'ghi\n')
>t = ('some long paragraph spanning multiple lines in an editor, '
>     'without newlines')

Is pretty common in code I see all the time.  I'm not sure why; I use it
occasionally, but only very rarely.  A lot of folks like this style a lot
though from what I can tell.

>This looks and works much better than triple-quoted string literals,
>esp. when defining such string literals in indented code.

I also see this code a lot:

from textwrap import dedent

s = dedent("""\
        abc
        def
        ghi
        """)

I think having to deal with indentation could be a common reason why people
use implicit concatenation instead of TQS.

All things considered, I think the difficult-to-spot bugginess of implicit
concatenation outweighs the occasional convenience of it.

-Barry
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