Python的Object基类的__init__方法
Python的Object基类的__init__方法
Python的__init__方法是用来初始化的实例的，是在__new__()方法执行后但是还没有return的情况下执行的__init__()方法。__new__()方法是用来创建实例的。这个__init__类似于构造方法，是可以直接从object类中继承的。如果一个BaseClass有__init__()方法，那么他的派生类(子类)需要显示的执行这个方法，不然是无法初始化BaseClass类的属性。__init__()方法是没有返回值的，并且如果有除了self意外的参数的话，在调用时是需要指定的。
创建类：
class Mytest1:
def __init__(self,value):
self._value = value
self._children = []
def myprint(self):
print('You point value : ',self._value)
if __name__ == '__main__':
t = Mytest1(1)
t.myprint()
输出：
You point value : 1
如果此时在实例化Mytest1时没有将value这个参数指定值，那么就会报错：
Traceback (most recent call last):
File "E:\workspace\mystudy\com\dgb\object\myinit.py", line 17, in
t = Mytest1()
TypeError: __init__() missing 1 required positional argument: 'value'
在父类和子类的环境中：
class Mytest1:
def __init__(self,value):
self._value = value
self._children = []
def myprint(self):
print('You point value : ',self._value)
class Mysubtest1(Mytest1):
def __init__(self,value,value1):
Mytest1.__init__(self,value)
self._value1 = value1
def myprint1(self):
print('sub class _value1 : ',self._value1)
print('base class _value : ',self._value)
if __name__ == '__main__':
t = Mytest1(1)
t.myprint()
ts = Mysubtest1(1,10)
ts.myprint1()
如果在Mysubtest1中init方法中没有调用父类的init方法的情况下是无法访问Mytest1中的_value属性的：
Traceback (most recent call last):
File "E:\workspace\mystudy\com\dgb\object\myinit.py", line 30, in
ts.myprint1()
File "E:\workspace\mystudy\com\dgb\object\myinit.py", line 23, in myprint1
print('base class _value : ',self._value)
AttributeError: 'Mysubtest1' object has no attribute '_value'
Python3.4版本中文档：
object. __init__ ( self [, ... ] )Called after the instance has been created (by __new__()), but before it is returned to the caller. The arguments are those passed to the class constructor expression. If a base class has an__init__() method, the derived class’s__init__() method, if any, must explicitly call it to ensure proper initialization of the base class part of the instance; for example: BaseClass.__init__(self,[args...]).
Because __new__() and __init__() work together in constructing objects (__new__() to create it, and __init__() to customise it), no non-None value may be returned by__init__(); doing so will cause aTypeError to be raised at runtime
开始系统的学习Python，从底层开始，夯实基础啊。一点一点积累。