44、class类：

一、类定义的一般形式：

1、简单的形式：实例化对象没有自己独有的数据属性。

>>> class fistclass():

... data1 = 'hello world' ### ==>这是类的数据属性或类成员属性。

... def printdata(self): ###==>这是类的方法，而且这里至少有一个参数self！！！

... print('nihao%s' %self.data1)

...

>>> class1 = fistclass() ##==>类实例化

>>> class1.

class1.__class__( class1.__format__( class1.__le__( class1.__reduce_ex__( class1.__weakref__

class1.__delattr__( class1.__ge__( class1.__lt__( class1.__repr__( class1.data1

class1.__dict__ class1.__getattribute__( class1.__module__ class1.__setattr__( class1.printdata(

class1.__dir__( class1.__gt__( class1.__ne__( class1.__sizeof__(

class1.__doc__ class1.__hash__( class1.__new__( class1.__str__(

class1.__eq__( class1.__init__( class1.__reduce__( class1.__subclasshook__(

>>> class1.data1 ##类数据属性调用

'hello world'

>>> class1.printdata() ##类的方法的调用

nihaohello world

2、定义对象独有的数据属性：

>>> class seclass():

... data1 = 'hello seclass'

... def setdata(self,x):

... self.str1 = x

... def printdata(self):

... print(self.str1)

...

>>> ins1 = seclass()

>>> ins1.

ins1.__class__( ins1.__format__( ins1.__le__( ins1.__reduce_ex__( ins1.__weakref__

ins1.__delattr__( ins1.__ge__( ins1.__lt__( ins1.__repr__( ins1.data1

ins1.__dict__ ins1.__getattribute__( ins1.__module__ ins1.__setattr__( ins1.printdata(

ins1.__dir__( ins1.__gt__( ins1.__ne__( ins1.__sizeof__( ins1.setdata(

ins1.__doc__ ins1.__hash__( ins1.__new__( ins1.__str__(

ins1.__eq__( ins1.__init__( ins1.__reduce__( ins1.__subclasshook__(

>>> ins1.data1

'hello seclass'

>>> ins1.setdata('abc')

>>> ins1.printdata()

abc

>>> ins2 = seclass()

>>> ins2.data1

'hello seclass'

>>> ins2.setdata('xy')

>>> ins2.printdata()

xy

3、__init__()方法：

创建实例时，python会自动调用类中的__init__方法，以隐性的为实例提供属性。

__init__称之为构造器。

如果类中没有定义__init__方法，则实例之初仅仅是创建一个简单的名称空间。

>>> class thirdclass():

... data3 = 'hello thirdclass'

... def __init__(self,who):

... self.name = who

...

>>> ins3 = thirdclass('lucy')

>>> ins3.

ins3.__class__( ins3.__format__( ins3.__le__( ins3.__reduce_ex__( ins3.__weakref__

ins3.__delattr__( ins3.__ge__( ins3.__lt__( ins3.__repr__( ins3.data3

ins3.__dict__ ins3.__getattribute__( ins3.__module__ ins3.__setattr__( ins3.name

ins3.__dir__( ins3.__gt__( ins3.__ne__( ins3.__sizeof__(

ins3.__doc__ ins3.__hash__( ins3.__new__( ins3.__str__(

ins3.__eq__( ins3.__init__( ins3.__reduce__( ins3.__subclasshook__(

>>> ins3.data3

'hello thirdclass'

>>> ins3.name

'lucy'

4、__dict__:

>>> ins3.__dict__ 实例的属性

{'name': 'lucy'}

>>> thirdclass.__dict__ 类的属性。

mappingproxy({'data3': 'hello thirdclass', '__init__': , '__dict__': , '__module__': '__main__', '__doc__': None, '__weakref__': })

5、类中的可用变量：

>>> class c1():

... var1 = 'hello c1' ###==>类的静态变量！！！！

... def __init__(self,who):

... self.insdata = who ###==>实例变量。

... self.name = '123' ###==>局部变量：只属于这个方法。

...

>>> ins1 = c1(12)

>>> ins1.

ins1.__class__( ins1.__format__( ins1.__le__( ins1.__reduce_ex__( ins1.__weakref__

ins1.__delattr__( ins1.__ge__( ins1.__lt__( ins1.__repr__( ins1.insdata

ins1.__dict__ ins1.__getattribute__( ins1.__module__ ins1.__setattr__( ins1.name

ins1.__dir__( ins1.__gt__( ins1.__ne__( ins1.__sizeof__( ins1.var1

ins1.__doc__ ins1.__hash__( ins1.__new__( ins1.__str__(

ins1.__eq__( ins1.__init__( ins1.__reduce__( ins1.__subclasshook__(

>>> ins1.name

'123'

>>> ins1.var1

'hello c1'

>>> ins1.insdata

12

6、类的继承：python允许多重继承，属性搜索方法：从左往右，从下往上。

>>> class PClass(object):

... gender = 'male'

... def __init__(self,who):

... self.name = who

...

>>> class CClass(PClass):

... def displayinfo(self):

... print(self.gender,self.name)

...

>>> ins1 = CClass('lucy')

>>> ins1.

ins1.__class__( ins1.__format__( ins1.__le__( ins1.__reduce_ex__( ins1.__weakref__

ins1.__delattr__( ins1.__ge__( ins1.__lt__( ins1.__repr__( ins1.displayinfo(

ins1.__dict__ ins1.__getattribute__( ins1.__module__ ins1.__setattr__( ins1.gender

ins1.__dir__( ins1.__gt__( ins1.__ne__( ins1.__sizeof__( ins1.name

ins1.__doc__ ins1.__hash__( ins1.__new__( ins1.__str__(

ins1.__eq__( ins1.__init__( ins1.__reduce__( ins1.__subclasshook__(

>>> ins1.gender

'male'

>>> ins1.name

'lucy'

>>> ins1.displayinfo()

male lucy