Given a class structure like this:
class A:
dependencies = ["x", "y"]
class B(A):
dependencies = ["z"]
class C(A):
dependencies = ["n", "m"]
class D(C):
dependencies = ["o"]
I want to know if it's possible to write a function (preferably living on class A) that does something along these lines:
@classmethod
def get_all_dependencies(cls):
return super().get_all_dependencies() + cls.dependencies
For the above classes, the expected output would be:
>>> A.get_all_dependencies():
["x", "y"]
>>> B.get_all_dependencies():
["x", "y", "z"]
>>> C.get_all_dependencies():
["x", "y", "n", "m"]
>>> D.get_all_dependencies():
["x", "y", "n", "m", "o"]
Obviously the above code doesn't work - it just returns the dependencies of the class I call it on. I'm not sure how to get it to work recursively across all the classes? (I'm eliding a hasattr check to ensure the parent class call get_all_dependencies().)
Walk the mro and grab the dependencies is what I'd do:
@classmethod
def get_dep(cls):
return [d for c in cls.mro()[:-1] for d in getattr(c, 'dependencies')]
with cls.mro()[:-1] being used to exclude object.
This returns:
>>> A.get_dep()
['x', 'y']
>>> B.get_dep()
['z', 'x', 'y']
>>> C.get_dep()
['n', 'm', 'x', 'y']
>>> D.get_dep()
['o', 'n', 'm', 'x', 'y']
Walk the MRO manually:
@classmethod
def get_all_dependencies(cls):
deps = []
for c in cls.__mro__:
# Manual dict lookup to not pick up inherited attributes
deps += c.__dict__.get('dependencies', [])
return deps
If you want to deduplicate dependencies that appear repeatedly in the MRO, you can:
from collections import OrderedDict
@classmethod
def get_all_dependencies(cls):
return list(OrderedDict.fromkeys(dep for c in cls.__mro__
for dep in c.__dict__.get('dependencies', [])))
You can certainly do this if you define "get_all_dependencies" on each class and, instead of cls.dependencies, you reference the class that you're on (ie. super(B, self).get_all_dependences() + B.dependencies)
