Re: [code-quality] [Python-ideas] Implicit string literal concatenation considered harmful?

On 11/05/2013 01:57, Ian Cordasco wrote:

On May 10, 2013 7:51 PM, "Nick Coghlan" mailto:ncoghlan@gmail.com> wrote:

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On 11 May 2013 04:50, "Guido van Rossum"

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I just spent a few minutes staring at a bug caused by a missing comma -- I got a mysterious argument count error because instead of foo('a', 'b') I had written foo('a' 'b').

This is a fairly common mistake, and IIRC at Google we even had a lint rule against this (there was also a Python dialect used for some specific purpose where this was explicitly forbidden).

Now, with modern compiler technology, we can (and in fact do) evaluate compile-time string literal concatenation with the '+' operator, so there's really no reason to support 'a' 'b' any more. (The reason was always rather flimsy; I copied it from C but the reason why it's needed there doesn't really apply to Python, as it is mostly useful inside macros.)

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

I could live with it if we get "dedent()" as a string method. I'd be even happier if constant folding was extended to platform independent method calls on literals, but I don't believe there's a sane way to

mailto:guido@python.org> wrote: maintain the "platform independent" constraint.

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OTOH, it's almost on the scale of "remove string mod formatting".

Shipping at least a basic linting tool in the stdlib would probably be almost as effective and substantially less disruptive. lib2to3 should provide some decent infrastructure for that.

I have cc'd the code-quality mailing list since several linger authors are subscribed there.

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I originally thought this was dangerous, and then changed my mind, and find this very useful when wrapping long strings to fit in 80 columns. I'll typically use such wrapping on SQL statements: cursor.execute('SELECT foo, bar FROM mytable ' 'WHERE baz = %(baz)s', {'baz': baz}) If you have a check for the number of mandatory arguments of a callable, you will catch some of the issues caused by this (not all of them though...) Then it's all a matter of the coding standards in your project / organization. So having a check for this in the various code checkers could probably be a nice addition, as long as it can be deactivated. -- Alexandre Fayolle