Python中类的定义、继承及使用对象实例详解
本文实例讲述了Python中类的定义、继承及使用对象的方法。分享给大家供大家参考。具体分析如下：
Python编程中类的概念可以比作是某种类型集合的描述，如“人类”可以被看作一个类，然后用人类这个类定义出每个具体的人——你、我、他等作为其对象。类还拥有属性和功能，属性即类本身的一些特性，如人类有名字、身高和体重等属性，而具体值则会根据每个人的不同；功能则是类所能实现的行为，如人类拥有吃饭、走路和睡觉等功能。具体的形式如下：
例：类的概念：
class 人类:
名字 = '未命名' # 成员变量
def 说话(内容): # 成员函数
print 内容 # 成员变量赋初始值
某人 = 人类() # 定义一个人类对象某人
某人.名字 = "路人甲"
某人.说话 ('大家好') # 路人甲说话
>>> 大家好！ # 输出
示例程序一（类的定义）：
>>> class pp: ... pass ... >>> p = pp() >>> print p <__main__.pp instance at 0x00CA77B0> >>>
打印了这个变量的类型。它告诉我们我们已经在__main__模块中有了一个Person类的实例。
示例程序二（__init__用法）：
说明：__init__方法在类的对象被建立时，马上运行。该方法用来对对象进行初始化。
>>> class Person:
... def __init__(self, name):
... self.name = name
... def sayHi(self):
... print 'Hello, my name is', self.name
...
>>> p = Person('Swaroop')
>>> p.sayHi()
Hello, my name is Swaroop
>>>示例程序三（__del__方法）：
说明：__del__方法是在程序退出时调用的。
>>> class Person:
... population = 0
... def __init__(self, name):
... self.name = name
... print '(Initializing %s)' % self.name
... def __del__(self):
... print '%s says bye.' % self.name
... Person.population -= 1
...
... def howMany(self):
... if Person.population == 1:
... print 'I am the only person here.'
... else:
... print 'We have %d persons here.' % Person.population
...
>>> A = Person('aa')
(Initializing aa)
>>> A.howMany()
We have 0 persons here.
>>> B = Person('bb')
(Initializing bb)
>>> B.howMany()
We have 0 persons here.
>>> ^Z
aa says bye.
bb says bye.Python中定义和使用类的形式为：class 类名[(父类名)]:[成员函数及成员变量]，类名为这个类的名称，而父类名为可选，但定义父类名后，子类则拥有父类的相应属性和方法。在用类定义成对象时，会先调用__init__构造函数，以初始化对象的各属性，类的各属性（成员变量）均可以在构造函数中定义，定义时只要加上对象指针就好了。而在对象销毁时，则会调用__del__析构函数，定义类的成员函数时，必须默认一个变量（类似于C++中的this指针）代表类定义的对象本身，这个变量的名称可自行定义，下面例子将使用self变量表示类对象变量。
例：类定义及使用：
class CAnimal:
name = 'unname'
# 成员变量
def __init__(self,voice='hello'):
# 重载构造函数
self.voice = voice
# 创建成员变量并赋初始值
def __del__(self):
# 重载析构函数
pass # 空操作
def Say(self):
print self.voice
t = CAnimal() # 定义动物对象t
t.Say() # t说话
>> hello # 输出
dog = CAnimal('wow') # 定义动物对象dog
dog.Say() # dog说话
>> wow # 输出Python编程中类可以承继父类属性，形式为class 类名（父类），子类可以继承父类的所有方法和属性，也可以重载父类的成员函数及属性，须注意的是子类成员函数若重载父类（即名字相同），则会使用子类成员函数
例：类的继承
class CAnimal:
def __init__(self,voice='hello'):
# voice初始化默认为hello
self.voice = voice
def Say(self):
print self.voice
def Run(self):
pass # 空操作语句（不做任何操作）
class CDog(CAnimal): # 继承类CAnimal
def SetVoice(self,voice): # 子类增加函数
SetVoice self.voice = voice
def Run(self,voice): # 子类重载函数Run
print 'Running'
bobo = CDog()
bobo.SetVoice('My Name is BoBo!')
# 设置child.data为hello
bobo.Say()
bobo.Run()
>> My Name is BoBo!
>> Running希望本文所述对大家的Python程序设计有所帮助。
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