Python MRO C3算法实现

wyyy721

　　算法实现

#-*- encoding:GBK -*-#
def mro_C3(*cls):
if len(cls)==1:
if not cls[0].__bases__:
return  cls
else:
return cls+ mro_C3(*cls[0].__bases__)
else:
seqs = [list(mro_C3(C)) for C in cls ] +[list(cls)]
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("inconsistent hierarchy, no C3 MRO is possible")
res.append(candidate)
for seq in non_empty:
if seq[0] == candidate:
del seq[0]
 　　测试一

#####################测试1
ob=object
class A(ob):
pass
class B(ob):
pass
class X(A,B):
pass
class Y(A,B):
pass
try:
class Z(X,Y):
pass
print Z.mro()
print Z.__mro__
print mro_C3(Z)
except :pass
try:
print mro_C3(X,Y)#如果从X,Y继承，它的MRO值是什么
except Exception,e:
print e
######打印结果
[<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.Y'>, <class '__main__.A'>, <class '__main__.B'>, <type 'object'>]
(<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.Y'>, <class '__main__.A'>, <class '__main__.B'>, <type 'object'>)
(<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.Y'>, <class '__main__.A'>, <class '__main__.B'>, <type 'object'>)
(<class '__main__.X'>, <class '__main__.Y'>, <class '__main__.A'>, <class '__main__.B'>, <type 'object'>)

 　　测试二

#####################测试2
ob=object
class A(ob):
pass
class B(ob):
pass
class X(A):
pass
class Y(B):
pass
try:
class Z(X,Y):
pass
print Z.mro()
print Z.__mro__
print mro_C3(Z)
except :pass
try:
print mro_C3(X,Y)#如果从A,B继承，它的MRO值是什么
except Exception,e:
print e
####打印结果
[<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.A'>, <class '__main__.Y'>, <class '__main__.B'>, <type 'object'>]
(<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.A'>, <class '__main__.Y'>, <class '__main__.B'>, <type 'object'>)
(<class '__main__.Z'>, <class '__main__.X'>, <class '__main__.A'>, <class '__main__.Y'>, <class '__main__.B'>, <type 'object'>)
(<class '__main__.X'>, <class '__main__.A'>, <class '__main__.Y'>, <class '__main__.B'>, <type 'object'>)

 　　测试三

#####################测试3

ob=object
class A(ob):
pass
class B(ob):
pass
class X(A,B):
pass
class Y(B,A):
pass
try:
class Z(X,Y):
pass
print Z.mro()
print Z.__mro__
print mro_C3(Z)
except :pass
try:
print mro_C3(X,Y)#如果从A,B继承，它的MRO值是什么
except Exception,e:
print e
##打印结果  报错了，无法 定义 类 Z
inconsistent hierarchy, no C3 MRO is possible