背景
- 有場景分別定義兩組邏輯，隨后有統一入口做基類屬性的整合
- 其中兩組邏輯的積累構造函數定義入參不同
- 設計類繼承圖如：
- 實際的使用方式抽象為[使用] 小節
- 實際開發過程中遇到問題
先說結論
- python 多繼承，需要使用super函數進行MRO的依次不重復初始化
- python 多繼承的情況下，構造函數__init__會被依次調用並傳遞參數
- python 多繼承情況下，__init__參數需要保持一致，否則會出現某些繼承路徑上的基類初始化遇到異常
- python 多繼承情況下，若構造函數參數不一致，可通過(*args, **kwargs)來統一
- python 多繼承情況下，若有公共基類，MRO可被調整為有跳躍路徑，進而利用子類不同的構造函數完成正常初始化，但需要臨近基類可以處理子類傳來的所有參數。
使用
# 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])
期望結果
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
第一版實現
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"
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'
第二版實現
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"
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'
二次繼承實現
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"
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
公共基類實現
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"
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實現
- 分別保持各自定義邏輯
- 在入口子類中，聲明沖突基類的對象，利用python的vars和__dict__的特性進行屬性的聲明
- 相當於手動hard-code 構造函數的調用，完成基類的初始化
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"
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
官方建議實現
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
結論
