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

Antoine Pitrou solipsis at pitrou.net
Fri May 10 21:16:13 CEST 2013


On Fri, 10 May 2013 11:48:51 -0700
Guido van Rossum <guido at python.org> wrote:
> 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'm rather -1. It's quite convenient and I don't want to add some '+'
signs everywhere I use it. I'm sure many people also have long string
literals out there and will have to endure the pain of a dull task to
"fix" their code.

However, in your case, foo('a' 'b') could raise a SyntaxWarning, since
the "continuation" is on the same line.

Regards

Antoine.





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