merits of Lisp vs Python

[Kirk Sluder]

In article 
<pan.2006.12.10.14.24.05.648068 at REMOVE.THIS.cybersource.com.au>,
 Steven D'Aprano <steve at REMOVE.THIS.cybersource.com.au> wrote:

> Yes. But you can't redefine 1+2 in Python, at least not without hacking
> the interpreter. Can you redefine (+ 1 2) in Lisp? 

Not without barreling through error messages about name conflicts.