http://pypy.org/performance.html http://pypy.org/performance.html says "String concatenation is expensive" and suggests using join() in loops. Its an old probl

http://pypy.org/performance.html http://pypy.org/performance.html says "String concatenation is expensive" and suggests using join() in loops. Its an old problem https://bitbucket.org/pypy/pypy/issues/1925/very-slow-string-concatenation https://bitbucket.org/pypy/pypy/issues/1925/very-slow-string... So whilst pypy is otherwise much faster than CPython, its missing of this kind of optimisation is why actually CPython can be faster for parsing my logs. I know about this because I've been bitten by it :)