Python面向对象class类属性及子类用法分析

时间:2022-09-14 13:59:24

本文实例讲述了Python面向对象class类属性及子类用法。分享给大家供大家参考,具体如下:

class类属性

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class Foo(object):
  x=1.5
foo=Foo()
print foo.x#通过实例访问类属性
>>>1.5
print Foo.x #通过类访问类属性
>>>1.5
foo.x=1.7  #只改新实例属性,不会改变类属性
print foo.x
>>>1.7
print Foo.x
>>>1.5
foo.x+=0.2 ##只改新实例属性,不会改变类属性
print foo.x
>>>1.9
print Foo.x
>>>1.5
del foo.x ##删除更新的实例属性,默认变为类的属性
print foo.x
>>>1.5
print Foo.x
>>>1.5

class子类

父类:

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class AddrBookEntry(object):
  "address book entry class"
  def __init__(self, nm, ph):
    self.name = nm
    self.phone = ph
    print "created instance for:", self.name
  def updatePhone(self, newph):
    self.phone = newph
    print "updated phone# for:", self.name

子类:

当一个类被派生出来,子类就继承了基类的属性。所以EmplAddrBookEntry继承了AddrBookEntry的updatePhone的方法。子类最好自定义自己的构造器,不然基类的构造器会被调用。如果子类重写了基类的构造器,基类的构造器就不会自动调用,除非被显示声明出来。

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class EmplAddrBookEntry(AddrBookEntry):
  "employee address book entry class"
  def __init__(self, nm, ph, id, em):##重写基类构造器
    AddrBookEntry.__init__(self, nm, ph)
    self.empid = id
    self.email = em
  def updateEmail(self, newem):
    self.email = newem
    print "updated e-mail address for:", self.name

使用子类:

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john = EmplAddrBookEntry("john doe","408-555-1212", 42, "john@spam.doe")
created instance for: john doe
>>> john
<__main__.EmplAddrBookEntry object at 0x02115FD0>
>>> john.name
'john doe'
>>> john.phone
'408-555-1212'
>>> john.email
'john@spam.doe'
>>> john.updatePhone("415-555-1212")
updated phone# for: john doe
>>> john.phone
'415-555-1212'
>>> john.updateEmail("john@doe.spam")
updated e-mail address for: john doe
>>> john.email
'john@doe.spam'

希望本文所述对大家Python程序设计有所帮助。

原文链接:http://www.cnblogs.com/paulwinflo/p/4991435.html