[Python-3000] Poll: Lazy Unicode Strings For Py3k

[Larry Hastings]

Josiah Carlson wrote:
> Perhaps I missed something about the concatenation implementation, but in order to prevent the rendering of lazy concatenation objects, shouldn't you need to keep a reference and pointer to the left and right strings/concatenation objects?  This isn't the same as a (small) slice holding onto a reference to a (big) string, but there is still an object lifetime consideration.
>   
You didn't miss anything--your summary is correct.  The lazy 
concatenation object holds references to both the left and right 
objects.  Since this isn't wasting memory, and it doesn't change 
Python's memory allocation behavior in any significant way (apart from 
the aforementioned able-to-fail APIs), I omitted it.

> P.P.S. I'm not certain, but I believe the V2 lazy slicing could be cleaned up with the use of weak references.
That's an interesting point.  They would simplify the implementation 
slightly, though perhaps not as much as you'd hope.  I think I'd still 
need much of the existing code in order to solve the really nasty 
boundary case (when the original string goes away during low-memory 
conditions).

Also consider: weak references would add their own overhead to the 
implementation.  In particular, weakref callbacks are on Python objects, 
so it always builds a tuple and calls via PyObject_Call().

In the final analysis I'm not sure a weakref-based implementation would 
make V2 lazy slicing any more palatable to the discerning Py3k core dev 
community.


/larry/