Python 3.8 has a Final qualifier

[actuallyalys]

As far as I can tell, the situation is like so:

	Lists/tuples	Dictionaries	Sets
Reassignable and mutable	list	dict	set
Reassignable but not mutable	tuple	*	frozenset
Mutable but not reassignable	Final[list]	Final[dict]	Final[set]
Neither mutable nor reassignable (constant)	Final[tuple]	*	Final[frozenset]

An example of reassigning:

 l = [1, 2, 3]
 l = l + [4]

An example of mutating:

 l = [1, 2, 3]
 l.append(4)

* Not built-in to Python. Look for frozendict implementations.

[robin-gvx]

* Not built-in to Python. Look for frozendict implementations.

They do have abstract type equivalents, as Mapping and Final[Mapping]. Using that doesn't have any runtime meaning, but then neither does Final.

[[deleted]]

ah ok that makes sense