问题
Suppose I have four classes: A
, B
derived from A
, C
derived from A
, and D
derived from C
. (So I always have single inheritance.)
In python, what is the best way to determine the closest common ancestor of any two (instances of such) classes? Specifically, I need a function clcoancl(X,Y)
for which clcoancl(A, B) == A
, clcoancl(B, C) == A
, and clcoancl(C, D) == C
.
回答1:
This should work for single or multiple inheritance, with any number of classes as input:
import inspect
from collections import defaultdict
def clcoancl(*cls_list):
mros = [list(inspect.getmro(cls)) for cls in cls_list]
track = defaultdict(int)
while mros:
for mro in mros:
cur = mro.pop(0)
track[cur] += 1
if track[cur] == len(cls_list):
return cur
if len(mro) == 0:
mros.remove(mro)
return None # or raise, if that's more appropriate
As both NPE and Daniel Rossman have mentioned though, this is probably not the optimal solution to your root problem.
回答2:
class A(object): pass
class B(A): pass
class C(A): pass
class D(C): pass
# get the list of ancestors (assuming single inheritance!)
def ancl(cls):
ret = []
while cls is not object:
ret.append(cls)
cls = cls.__bases__[0]
ret.append(object)
return ret
def clcoancl(cls1, cls2):
ancl1 = ancl(cls1)
ancl2 = ancl(cls2)
# find the first class present in both ancl1 and ancl2
while len(ancl1) > 0 and len(ancl2) > 0 and ancl1[-1] == ancl2[-1]:
ret = ancl1.pop(-1)
ancl2.pop(-1)
return ret
print clcoancl(A, B)
print clcoancl(B, C)
print clcoancl(C, D)
Whether you actually need this is a different matter, as pointed out by @DanielRoseman is his comment to your question.
来源:https://stackoverflow.com/questions/15788725/how-to-determine-the-closest-common-ancestor-class