Hi!

A thread in PyAr raised the question that, considering that strings are immutable, why a slice of a string is a copy and not a reference to a part of that string.

I couldn't answer why, so I'm asking here...Is it because the reference counting will be complicated? Is it because it'd be inefficient in other way? It's something else? Or is something that could be done... but is not done yet?

Thank you very much!

We implemented this feature in pypy. It's turned of by default, because nobody could come out with a real world example benefiting from it. Regarding worst-case scenario, we only create this special object if slice length is not shorter than some percentage of source string (I think 75%, can be tuned). You still need to pay for a dispatch (even if small price) wherever you use string, to check if this is special object or not. Cheers, fijal