[Python-Dev] PEP 498: Literal String Interpolation is ready for pronouncement

[haypo s]

2015-09-05 5:01 GMT+02:00 Guido van Rossum <guido at 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