[Python-Dev] PEP 0008 confusion - here it is, but don't use it?

[Tim Peters]

>> For example, do not rely on CPython's efficient implementation
>>       of in-place string concatenation for statements in the form a+=b or
>>       a=a+b.  Those statements run more slowly in Jython.

[Phillip J. Eby]
> Is that really true?  I thought the last time this came up, somebody said
> that common Java implementations actually had special case code to speed up
> string concatenation.

Java != Jython.  Java compilers know when they're dealing with
strings, and the Java spec defines '+' on strings in terms of
mutable-StringBuffer operations.  Even so, the pragmatics of string
concatenation in Java are complex, well illustrated by this
excruciating "tech tip":

    http://java.sun.com/developer/JDCTechTips/2002/tt0305.html

Jython is as blind as Python at compile-time about what the types are
in "a=a+b".