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@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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