cPython, IronPython, Jython, and PyPy (Oh my!)

[Ethan Furman]

Just hit a snag:

In cPython the deterministic garbage collection allows me a particular 
optimization when retrieving records from a dbf file -- namely, by using 
weakrefs I can tell if the record is still in memory and active, and if 
so not hit the disk to get the data;  with PyPy (and probably the 
others) this doesn't work because the record may still be around even 
when it is no longer active because it hasn't been garbage collected yet.

For PyPy I can use `'PyPy' in sys.version` to set a constant 
(REFRESH_FROM_DISK in this case) to disable the cPython optimization; 
does anyone know what strings to look for for the other implementations?

~Ethan~