python多继承构造函数声明问题
前言：
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背景
有场景分别定义两组逻辑，随后有统一入口做基类属性的整合
其中两组逻辑的积累构造函数定义入参不同
设计类继承图如：
-
实际的使用方式抽象为[使用] 小节
-
实际开发过程中遇到问题
先说结论
-
python 多继承，需要使用super函数进行MRO的依次不重复初始化
-
python 多继承的情况下，构造函数__init__会被依次调用并传递参数
-
python 多继承情况下，__init__参数需要保持一致，否则会出现某些继承路径上的基类初始化遇到异常
-
python 多继承情况下，若构造函数参数不一致，可通过(*args, **kwargs)来统一
-
python 多继承情况下，若有公共基类，MRO可被调整为有跳跃路径，进而利用子类不同的构造函数完成正常初始化，但需要临近基类可以处理子类传来的所有参数。
使用
'''
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'''
# tjc = TestJobConfiger()
tjc = SubTest()
print vars(tjc)
print "\n".join([tjc.base_key,
tjc.base1_key,
tjc.subbase_key,
tjc.subbase1_key,
tjc.subtest_key])
期望结果
enter Base
enter SubBase
enter Base1|_arg1 |_arg2
enter SubBase1|_arg1 |_arg2
vars : {'base1_key': 'base1_key', 'subtest_key': 'subtest_key', 'subbase1_key': 'subbase1_key', 'subbase_key': 'subbase_key', 'base_key': 'base_key'}
values: base_key
base1_key
subbase_key
subbase1_key
subtest_key
第一版实现
class Base(object):
def __init__(self):
print "enter Base"
self.base_key = "base_key"
class Base1(object):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
print "enter Base1" + "|" + _arg1 + "|" + _arg2
self.base1_key = "base1_key"
class SubBase(Base):
def __init__(self):
super(SubBase, self).__init__()
print "enter SubBase"
self.subbase_key = "subbase_key"
class SubBase1(Base1):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(SubBase1, self).__init__(_arg1 = _arg1, _arg2=_arg2)
print "enter SubBase1" + "|" + _arg1 + "|" + _arg2
self.subbase1_key = "subbase1_key"
class SubTest(SubBase,SubBase1):
def __init__(self, _arg1 = "_arg1 "):
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
# self.__dict__.update(vars(SubBase()))
self.subtest_key = "subtest_key"
运行结果为：
'''
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'''
Traceback (most recent call last):
File "/Users/enzhao/suanec/ksp/dispatch/weiclient/client/weiclient/libs/com/weibo/tools/job_manager/job_configer_tester.py", line 43, in <module>
tjc = SubTest()
File "/Users/enzhao/suanec/ksp/dispatch/weiclient/client/weiclient/libs/com/weibo/tools/job_manager/job_configer_tester.py", line 38, in __init__
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
TypeError: __init__() got an unexpected keyword argument '_arg1'
第二版实现
class Base(object):
def __init__(self):
print "enter Base"
self.base_key = "base_key"
class Base1(object):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
print "enter Base1" + "|" + _arg1 + "|" + _arg2
self.base1_key = "base1_key"
class SubBase(Base):
def __init__(self, **kwargs):
super(SubBase, self).__init__()
print "enter SubBase"
self.subbase_key = "subbase_key"
class SubBase1(Base1):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(SubBase1, self).__init__(_arg1 = _arg1, _arg2=_arg2)
print "enter SubBase1" + "|" + _arg1 + "|" + _arg2
self.subbase1_key = "subbase1_key"
class SubTest(SubBase,SubBase1):
def __init__(self, _arg1 = "_arg1 "):
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
# self.__dict__.update(vars(SubBase()))
self.subtest_key = "subtest_key"
运行结果为：
Traceback (most recent call last):
enter Base
enter SubBase
File "/Users/enzhao/suanec/ksp/dispatch/weiclient/client/weiclient/libs/com/weibo/tools/job_manager/job_configer_tester.py", line 46, in <module>
vars : {'subtest_key': 'subtest_key', 'subbase_key': 'subbase_key', 'base_key': 'base_key'}
tjc.base1_key,
AttributeError: 'SubTest' object has no attribute 'base1_key'
二次继承实现
'''
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'''
class Base(object):
def __init__(self):
print "enter Base"
self.base_key = "base_key"
class Base1(Base):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(Base1, self).__init__()
print "enter Base1" + "|" + _arg1 + "|" + _arg2
self.base1_key = "base1_key"
class SubBase(Base):
def __init__(self, **kwargs):
super(SubBase, self).__init__()
print "enter SubBase"
self.subbase_key = "subbase_key"
class SubBase1(Base1):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(SubBase1, self).__init__(_arg1 = _arg1, _arg2=_arg2)
print "enter SubBase1" + "|" + _arg1 + "|" + _arg2
self.subbase1_key = "subbase1_key"
class SubTest(SubBase,SubBase1):
def __init__(self, _arg1 = "_arg1 "):
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
# self.__dict__.update(vars(SubBase()))
self.subtest_key = "subtest_key"
运行结果为：
enter Base
enter Base1|_arg1 |_arg2
enter SubBase1|_arg1 |_arg2
enter SubBase
vars : {'base1_key': 'base1_key', 'subtest_key': 'subtest_key', 'subbase_key': 'subbase_key', 'subbase1_key': 'subbase1_key', 'base_key': 'base_key'}
values: base_key
base1_key
subbase_key
subbase1_key
subtest_key
公共基类实现
'''
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'''
class BBase(object):
def __init__(self):
pass
class Base(BBase):
def __init__(self):
print "enter Base"
self.base_key = "base_key"
class Base1(BBase):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
print "enter Base1" + "|" + _arg1 + "|" + _arg2
self.base1_key = "base1_key"
class SubBase(Base):
def __init__(self, **kwargs):
super(SubBase, self).__init__()
print "enter SubBase"
self.subbase_key = "subbase_key"
class SubBase1(Base1):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(SubBase1, self).__init__(_arg1 = _arg1, _arg2=_arg2)
print "enter SubBase1" + "|" + _arg1 + "|" + _arg2
self.subbase1_key = "subbase1_key"
class SubTest(SubBase,SubBase1):
def __init__(self, _arg1 = "_arg1 "):
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
# self.__dict__.update(vars(SubBase()))
self.subtest_key = "subtest_key"
运行结果为：
enter Base
enter SubBase
vars : {'subtest_key': 'subtest_key', 'subbase_key': 'subbase_key', 'base_key': 'base_key'}
Traceback (most recent call last):
File "/Users/enzhao/suanec/ksp/dispatch/weiclient/client/weiclient/libs/com/weibo/tools/job_manager/job_configer_tester.py", line 50, in <module>
tjc.base1_key,
AttributeError: 'SubTest' object has no attribute 'base1_key'
Hack实现
分别保持各自定义逻辑
在入口子类中，声明冲突基类的对象，利用python的vars和__dict__的特性进行属性的声明
相当于手动hard-code 构造函数的调用，完成基类的初始化
'''
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寻找有志同道合的小伙伴，互帮互助,群里还有不错的视频学习教程和PDF电子书！
'''
class Base(object):
def __init__(self):
print "enter Base"
self.base_key = "base_key"
class Base1(object):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
print "enter Base1" + "|" + _arg1 + "|" + _arg2
self.base1_key = "base1_key"
class SubBase(Base):
def __init__(self):
super(SubBase, self).__init__()
print "enter SubBase"
self.subbase_key = "subbase_key"
class SubBase1(Base1):
def __init__(self, _arg1 = "_arg1 ", _arg2 = "_arg2 "):
super(SubBase1, self).__init__(_arg1 = _arg1, _arg2=_arg2)
print "enter SubBase1" + "|" + _arg1 + "|" + _arg2
self.subbase1_key = "subbase1_key"
class SubTest(SubBase1):
def __init__(self, _arg1 = "_arg1 "):
super(SubTest, self).__init__(_arg1=_arg1, _arg2="None")
self.__dict__.update(vars(SubBase()))
self.subtest_key = "subtest_key"
运行结果为：
'''
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寻找有志同道合的小伙伴，互帮互助,群里还有不错的视频学习教程和PDF电子书！
'''
enter Base1|_arg1 |None
enter SubBase1|_arg1 |None
enter Base
enter SubBase
vars : {'base1_key': 'base1_key', 'subtest_key': 'subtest_key', 'subbase_key': 'subbase_key', 'subbase1_key': 'subbase1_key', 'base_key': 'base_key'}
values: base_key
base1_key
subbase_key
subbase1_key
subtest_key
官方建议实现
class A(object):
def __init__(self, *args, **kwargs):
print "A"
class B(object):
def __init__(self, *args, **kwargs):
print "B"
class C(A):
def __init__(self, arg, *args, **kwargs):
print "C","arg=",arg
super(C, self).__init__(arg, *args, **kwargs)
class D(B):
def __init__(self, arg, *args, **kwargs):
print "D", "arg=",arg
super(D, self).__init__(arg, *args, **kwargs)
class E(C,D):
def __init__(self, arg, *args, **kwargs):
print "E", "arg=",arg
super(E, self).__init__(arg, *args, **kwargs)
print "MRO:", [x.__name__ for x in E.__mro__]
E(10)
MRO: ['E', 'C', 'A', 'D', 'B', 'object']
E arg= 10
C arg= 10
A
尾语
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