python __mro__ c3算法

def mro_c3(*bases):
if len(bases) == 1:
if not bases[0].__bases__:
return bases
else:
return bases + mro_c3(*bases[0].__bases__)

else:
seqs = [list(mro_c3(C)) for C in bases] + [list(bases)]
res = []
while True:
non_empty = list(filter(None, seqs))
if not non_empty:
return tuple(res)
for seq in non_empty:
candidate = seq[0]
not_head = [ s for s in non_empty if candidate in s[1:]]
if not_head:
candidate = None
else:
break
if not candidate:
raise TypeError('adfadsf')
res.append(candidate)
for seq in non_empty:
if seq[0] == candidate:
del seq[0]

比如：

class A(object): pass
class B(dict ): pass
class CC(A, B): pass

求CC.__mro__步骤是：(下面mro既mro_c3)

(CC) + mro((A,B))

(CC)+[mro(A), mro(B)] + [[A, B]]

(CC) + [ (A, object), (B, dict, object), [A,B]] ==> res =[]

(CC) + [ ( object), (B, dict, object), [B]] ==> res =[A]

(CC) + [ (object), (B, dict, object), [B]] ==> res =[A] #object 没有被加进res

(CC) + [ (object), ( dict, object), []] ==> res =[A,B]

(CC) + [ (object), ( dict, object)] ==> res =[A,B] #object 没有被加进res

(CC) + [ (object), ( object)] ==> res =[A,B, dict]

(CC) + [ ] ==> res =[A,B, dict, object]

(CC) + res => (CC, A, B, dict, object)