fmap.py

import functools
import types


@functools.singledispatch
def fmap(value, fun):
    return value


@fmap.register(list)
def _(value, fun):
    return [fun(item) for item in value]


@fmap.register(dict)
def _(value, fun):
    return {key: fun(item) for key, item in value.items()}


@fmap.register(set)
def _(value, fun):
    return {fun(item) for item in value}


@fmap.register(types.FunctionType)
def _(value, fun):
    return lambda x: fun(value(x))


def add_suffix(s):
    return s + " world"


def upper(s):
    return s.upper()


print(fmap(["foo", "bar"], upper))
print(fmap({1: "foo", 2: "bar"}, upper))
print(fmap({"foo", "bar"}, upper))
print(fmap(add_suffix, upper)("Hello"))