Why not a Python compiler?

[Ryszard Szopa]

On Feb 5, 9:30 am, cokofree... at gmail.com wrote:

> I don't know the exact details but I think the issue is the dynamic
> nature of Python makes it impossible to correctly store the various
> types and changes into compiled code. Someone else will probably be
> able to provide a good reason as to why it isn't very feasible, nor a
> good idea. If you want to speed up your python look at Psyco. http://psyco.sourceforge.net/

Yeah, but exactly what features make it so hard to write a compiler
for Python?

Common Lisp seems like a language at least as dynamic as Python, e.g.
you can change the type of objects at runtime, you can make changes to
functions, you can change classes at runtime, you can add methods and
generic functions (nb. these changes are reflected in existing
objects), you have a metaobject protocol. Moreover, you have
multimethods (in Python you don't, so it is one less thing to care).
However, Common Lisp has a few decent compilers (at least two open
source and two commercial).

Google tells me that such arguments have been raised back in 2001 [1].
I can add from myself that today Python is much more similar to Common
Lisp than in 2001. For example, multiple inheritance in Python >= 2.3
behaves like in Dylan, which in turn behaves like CLOS with a twist.

What is more, apparently there is a Python compiler via CL: CLPython
(I don't have access to ACL, however, so I can't verify the claims of
the authors).

Finally, speaking of JIT compilers: recently has appeared something
that looks like  avery nice JIT compiler for Scheme, Ikarus [3].
Scheme is also quite dynamical, but is not OO, so I don't know how
viable is the analogy.

Of course, when writing Python extensions in C is fairly easy and when
rewriting just the critical part of the code is enough to get
acceptable performance, I really doubt I will see anybody willing to
invest serious amounts of money and time into writing a native
compiler for Python. Learning C cannot be so hard ;-). Also, this
seems consistent with Python viewed as a glue between libraries
written in C.


Cheers,

    -- Richard

BIG FAT DISCLAIMER: I DO NOT want to start a "Python vs. Common Lisp
and Scheme" flame war.

[1] http://mail.python.org/pipermail/python-list/2001-April/080394.html
[2] http://common-lisp.net/project/clpython/
[3] http://www.cs.indiana.edu/~aghuloum/ikarus/