Different ways to resolve dependencies

deps.py

# Manual constructor injection

class Charlie:
    pass

class Beta:
    def __init__(self, charlie):
        self.charlie = charlie

class Alpha:
    def __init__(self, beta):
        self.beta = beta

a = Alpha(Beta(Charlie()))

# Manual setter injection

a = A()
a.x = 1

# Factory

class Charlie:
    pass

class Beta:
    def __init__(self, charlie):
        self.charlie = charlie

class Alpha:
    def __init__(self, beta):
        self.beta = beta

class BetaFactory:
    def make(self):
        return Beta(Charlie())

class AlphaFactory:
    def make(self):
        return Alpha(BetaFactory().make())

a = AlphaFactory().make()

# ???

class Charlie:
    pass

class Beta:
    def __init__(self):
        self.charlie = Charlie()

class Alpha:
    def __init__(self):
        self.beta = Beta()

a = Alpha()