Backwards emulation rather than backwards compatibility?

[Kragen Sitaker]

Antaeus Feldspar <feldspar at ix.netcom.com> writes:
> Could the python interpreter be equipped with a mode that would allow it 
> to emulate past interpreters?  Thus, if someone needed access to a 
> script that was designed for 1.5.2, they could pass a "--1.5.2" argument 
> to the interpreter and have it run under 1.5.2's rules...

You'd really want it to be a per-module declaration, at which point it
becomes 'from __future__ import ...'.