Barbara Liskov wins Turing Award

"Martin v. Löwis" martin at
Thu Jun 25 15:25:07 EDT 2009

> Python's object model, assignment semantics, and call-by-object
> mechanism, and that name, come from CLU.  Whether Guido knew of it
> directly or not, I do not know. To the extent that the above is part of
> the heart of Python, I think Steven's statement stands pretty well.

Why do you say that? ISTM that Python is much closer to Smalltalk than
to CLU in its object model. CLU is statically typed (and it is important
to its notion of program correctness that it is statically typed);
Smalltalk and Python aren't. In addition, Smalltalk and Python have
inheritance; CLU (deliberately) doesn't. Liskov reported that she didn't
know about Smalltalk until 1976.

I believe that Python's, CLU's, and Smalltalk's assignment semantics
actually all come from Simula. I would claim the same for the
call-by-object mechanism - except that this is probably best described
as coming from LISP (in the sense of caller and callee sharing

FWIW, Simula has also inheritance, but that specific notion of
inheritance did not transfer to any other language, except for Beta.


More information about the Python-list mailing list