composition.py

class Composition:
    def __init__(self, *funcs):
        self._funcs = [*funcs]

    def append(self, obj):
        if isinstance(obj, Composition):
            self._funcs.extend(obj._funcs)
        elif callable(obj):
            self._funcs.append(obj)
        else:
            raise RuntimeError('Only Composition instances or callable objects can be appended to a class Composition.')

    def prepend(self, obj):
        if isinstance(obj, Composition):
            for func in obj._funcs:
                self._funcs.insert(0, func)
        elif callable(obj):
            self._funcs.insert(0, obj)
        else:
            raise RuntimeError('Only Composition instances or callable objects can be appended to a class Composition.')

    def __call__(self, *args, **kwargs):
        res = self._funcs[0](*args, **kwargs)
        for func in self._funcs[1:]:
            res = func(res)
        return res

    def __rshift__(self, other):
        # self >> other
        self.append(other)
        return self

    def __lshift__(self, other):
        # self << other
        self.prepend(other)
        return self

class ComposableFunc:
    def __init__(self, func):
        self.name = func.__name__
        self.func = func

    def __rshift__(self, other):
        # self >> other
        if isinstance(other, Composition):
            other.prepend(self)
            return other
        else:
            return Composition(self, other)

    def __lshift__(self, other):
        # self << other
        if isinstance(other, Composition):
            other.append(self)
            return other
        else:
            return Composition(other, self)

    def __call__(self, *args, **kwargs):
        return self.func(*args, **kwargs)

def composable(func):
    return ComposableFunc(func)

@composable
def ca(val):
    print('ca', val)
    return 'yay !'

@composable
def cb(val):
    print('cb', val)
    return val + 100

@composable
def cc(val1, val2, valk=None):
    print('cc', val1, val2, valk)
    return 20


cd = ca << cb << cc
cd = cc >> cb >> ca
cd = cb << cc >> ca
print(cd(10, 11, valk='hi'))