[Python-Dev] apparent ruminations on mutable immutables (was:PEP 351, the freeze protocol)

Noam Raphael noamraph at gmail.com
Tue Nov 1 22:20:34 CET 2005

On 11/1/05, Delaney, Timothy (Tim) <tdelaney at avaya.com> wrote:
> Noam,
> There's a simple solution to all this - write a competing PEP. One of
> the two competing PEPs may be accepted.

I will. It may take some time, though.
> FWIW, I'm +1 on PEP 351 in general, and -1 on what you've proposed.
> PEP 351 is simple to explain, simple to implement and leaves things
> under the control of the developer. I think there are still some issues
> to be resolved, but the basic premise is exactly what I would want of a
> freeze protocol.
> Tim Delaney

It is true that PEP 351 is simpler. The problem is, that thanks to PEP
351 I have found a fundamental place in which the current Python
design is not optimal. It is not easy to fix it, because 1) it would
require a significant change to the current implementation, and 2)
people are so used to the current design that it is hard to convince
them that it's flawed.

The fact that discussing the design is long doesn't mean that the
result, for the Python programmer, would be complicated. They won't -
my suggestion will cause almost no backward-compatibility problems.
Think about it - it clearly means that my suggestion simply can't make
Python programming *more* complicated.

Please consider new-style classes. I'm sure they required a great deal
of discussion, but they are simple to use -- and they are a good
thing. And I think that my suggestion would make things easier, more
than the new-style-classes change did. Features of new-style classes
are an advanced topic. The questions, "why can't I change my strings?"
"why do you need both a tuple and a list?" and maybe "why can't I add
my list to a set", are fundamental ones, which would all not be asked
at all if my suggestion is accepted.


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