[ianandrich]

> It might be possible to implement function purity with a decorator. (Kind of like declaring something “safe” in Rust).

Two parts to this. 1: Does it mutate variables. 2. Does the code have side effects.

1: def no_mut(func): @functools.wraps def new_func(args, *kwargs): new_args = tuple(copy.deepcopy(arg) for arg in args) new_kwargs = {k, copy.deepcopy(v) for k, v in *kwargs return func(new_args, *new_kwargs) return new_func

For the second point, gevent seemed to have a trick to identify side effecting code.