On Sat, Sep 5, 2015 at 1:44 AM, haypo s <victor.stin...@gmail.com> wrote:
> 2015-09-05 5:01 GMT+02:00 Guido van Rossum <gu...@python.org>: > > And I'm ready to accept it. I'll wait until Tuesday night (Monday's a > > holiday in the US) in case anything unforeseen comes up, but this is > really > > the Last Call for this PEP. > > String concatenation is inefficient in Python because strings are > immutable. There is a micro-optimization which tried to reduce the bad > performances of a+b, but it's better to avoid it. > > Python replaces >'abc' 'def'< with a single string >'abcdef'<. It's > done by the parser, there is no overhead at runtime. > > PEP 498 allows to write >'abc' f'string'< which is replaced with > >'abc' 'string'.__format__()< whereas str+str is a bad practice. > > I would prefer to force users to write an explicit '+' to remind them > that there are more efficient ways to concatenate strings like > ''.join((str1, str2)) or putting the first string in the f-string: > >f'abcstring'<. > > Section in the PEP: > https://www.python.org/dev/pepsstring/pep-0498/#concatenating-strings > > Victor > What does the extra + buy users? It's just more punctuation noise. The implementation is intentionally left unspecified by the PEP; it should be possible to design an implementation that combines all the parts together more efficiently than the use of + (e.g. using a "string builder" object internally). -- --Guido van Rossum (python.org/~guido)
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