[Python-ideas] "Immutable Builder" Pattern and Operator

[Wes Turner]

Have you looked at pyrsistent for
immutable/functional/persistent/copy-on-write data structures in Python?

https://github.com/tobgu/pyrsistent/

(freeze() / thaw())

... e.g. List and Dict NamedTuple values are not immutable (because
append() and update() still work)

On Sunday, January 22, 2017, Soni L. <fakedme+py at gmail.com> wrote:

> I've been thinking of an Immutable Builder pattern and an operator to go
> with it. Since the builder would be immutable, this wouldn't work:
>
> long_name = mkbuilder()
> long_name.seta(a)
> long_name.setb(b)
> y = long_name.build()
>
> Instead, you'd need something more like this:
>
> long_name = mkbuilder()
> long_name = long_name.seta(a)
> long_name = long_name.setb(b)
> y = long_name.build()
>
> Or we could add an operator to simplify it:
>
> long_name = mkbuilder()
> long_name .= seta(a)
> long_name .= setb(b)
> y = long_name.build()
>
> (Yes, I'm aware you can x = mkbuilder().seta(a).setb(b), then y =
> x.build(). But that doesn't work if you wanna "fork" the builder. Some
> builders, like a builder for network connections of some sort, would work
> best if they were immutable/forkable.)
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