新類型類中的方法解析順序(MRO)？在書中簡略的Python(第2版)有一個例子舊的樣式類來演示如何按照經(jīng)典的解析順序和與新秩序有何不同？通過用新樣式重寫示例，我嘗試了同一個示例，但結(jié)果與用舊樣式類獲得的結(jié)果沒有什么不同。我在運行示例時使用的python版本是2.5.2.下面是一個例子：class Base1(object):
def amethod(self): print "Base1" class Base2(Base1):
passclass Base3(object):
def amethod(self): print "Base3"class Derived(Base2,Base3):
passinstance = Derived() instance.amethod() print Derived.__mro__打電話instance.amethod()版畫Base1，但根據(jù)我對具有新類型類的MRO的理解，輸出應(yīng)該是Base3..打電話Derived.__mro__指紋：(<class '__main__.Derived'>, <class '__main__.Base2'>, <class '__main__.Base1'>, <class '__main__.Base3'>, <type 'object'>)我不確定我對MRO的理解是錯誤的，還是我做了一個我無法察覺的愚蠢的錯誤。請幫助我更好地理解MRO。
3 回答
蝴蝶刀刀
TA貢獻1801條經(jīng)驗 獲得超8個贊
class G():
def m(self):
print("G")class F(G):
def m(self):
print("F")
super().m()class E(G):
def m(self):
print("E")
super().m()class D(G):
def m(self):
print("D")
super().m()class C(E):
def m(self):
print("C")
super().m()class B(D, E, F):
def m(self):
print("B")
super().m()class A(B, C):
def m(self):
print("A")
super().m()# A^# / \# B^ C^# /| X# D^ E^ F^# \ | /# Gx = A()x.m()
class I(G):
def m(self):
print("I")
super().m()
class H():
def m(self):
print("H")
class G(H):
def m(self):
print("G")
super().m()
class F(H):
def m(self):
print("F")
super().m()
class E(H):
def m(self):
print("E")
super().m()
class D(F):
def m(self):
print("D")
super().m()
class C(E, F, G):
def m(self):
print("C")
super().m()
class B():
def m(self):
print("B")
super().m()
class A(B, C, D):
def m(self):
print("A")
super().m()
# Algorithm:
# 1. Build an inheritance graph such that the children point at the parents (you'll have to imagine the arrows are there) and
# keeping the correct left to right order. (I've marked methods that call super with ^)
# A^
# / | \
# / | \
# B^ C^ D^ I^
# / | \ / /
# / | X /
# / |/ \ /
# E^ F^ G^
# \ | /
# \ | /
# H
# (In this example, A is a child of B, so imagine an edge going FROM A TO B)
# 2. Remove all classes that aren't eventually inherited by A
# A^
# / | \
# / | \
# B^ C^ D^
# / | \ /
# / | X
# / |/ \
# E^ F^ G^
# \ | /
# \ | /
# H
# 3. For each level of the graph from bottom to top
# For each node in the level from right to left
# Remove all of the edges coming into the node except for the right-most one
# Remove all of the edges going out of the node except for the left-most one
# Level {H}
#
# A^
# / | \
# / | \
# B^ C^ D^
# / | \ /
# / | X
# / |/ \
# E^ F^ G^
# |
# |
# H
# Level {G F E}
#
# A^
# / | \
# / | \
# B^ C^ D^
# | \ /
# | X
# | | \
# E^F^ G^
# |
# |
# H
# Level {D C B}
#
# A^
# /| \
# / | \
# B^ C^ D^
# | |
# | |
# | |
# E^ F^ G^
# |
# |
# H
# Level {A}
#
# A^
# |
# |
# B^ C^ D^
# | |
# | |
# | |
# E^ F^ G^
# |
# |
# H
# The resolution order can now be determined by reading from top to bottom, left to right. A B C E D F G H
x = A()
x.m()
冉冉說
TA貢獻1877條經(jīng)驗 獲得超1個贊
Base3Base1
class Base1(object): def amethod(self): print "Base1"class Base2(Base1): passclass Base3(Base1): def amethod(self): print "Base3"class Derived(Base2,Base3): passinstance = Derived()instance.amethod()class Base1: def amethod(self): print "Base1"class Base2(Base1): passclass Base3(Base1): def amethod(self): print "Base3"class Derived(Base2,Base3): passinstance = Derived()instance.amethod()
Base3Base1
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