in response to https://mathstodon.xyz/@vez/111012730223951046

meta.py

from collections import UserList
from functools import partial
from operator import add

# a class that allows a subclass to declare a function to use to handle all protocols
class CustomApplyList(UserList):
    def __init__(self, f, args):
        super().__init__(args)
        self.f = f

    def __add__(self, n):
        self.data = self.f(partial(add, n), self.data)
        return self

    # XXX: implement other operator protocols here

    def __call__(self, g):
        self.data = self.f(g, self.data)
        return self

# which lets you define a class like this, with a function that describes how to apply functions to itself
class Mapper(CustomApplyList):
    def __init__(self, args):
        super().__init__(lambda data, f: list(map(data, f)), args)

usage.py

In [8]: m = Mapper([1,2,3])

In [9]: m + 1
Out[9]: Mapper([2, 3, 4])

In [10]: m(lambda x: x ** 2)
Out[10]: Mapper([4, 9, 16])