教为学：Python学习之路（六）：类
教为学：Python学习之路（六）：类类与对象
通俗点说类是定义，对象是实体。
简单点说人是类，高鹏我是对象。
属性
属性有实例属性和类属性之分。
先上一段代码看看：
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class Fruit:
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price = 0
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def __init__(self):
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self.color='red'
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zone="china"
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if __name__=="__main__":
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print "Fruit price:%d"%Fruit.price
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apple = Fruit()
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print "apple color:%s"%apple.color
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print "apple price:%d"%apple.price
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banane = Fruit()
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print "banane color:%s"%banane.color
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print "banane price:%d"%banane.price
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Fruit.color="yellow"
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Fruit.price=50
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print "apple color:%s"%apple.color
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print "apple price:%d"%apple.price
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print "banane color:%s"%banane.color
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print "banane price:%d"%banane.price
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#结果
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Fruit price:0
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apple color:red
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apple price:0
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banane color:red
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banane price:0
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apple color:red
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apple price:50
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banane color:red
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banane price:50
通过类可以直接修改所有类的类属性，却不可以修改实例属性。
修改17、18行上。
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class Fruit:
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price = 0
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def __init__(self):
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self.color='red'
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zone="china"
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if __name__=="__main__":
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print "Fruit price:%d"%Fruit.price
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apple = Fruit()
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print "apple color:%s"%apple.color
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print "apple price:%d"%apple.price
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banane = Fruit()
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print "banane color:%s"%banane.color
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print "banane price:%d"%banane.price
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apple.color="yellow"
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apple.price=50
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print "apple color:%s"%apple.color
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print "apple price:%d"%apple.price
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print "banane color:%s"%banane.color
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print "banane price:%d"%banane.price
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#结果
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Fruit price:0
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apple color:red
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apple price:0
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banane color:red
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banane price:0
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apple color:yellow
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apple price:50
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banane color:red
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banane price:0
对实例变量修改只影响本身实例变量和本实例的类属性。
再谈一句很搞笑的。
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class Fruit:
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price = 0
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def __init__(self):
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self.color='red'
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zone="china"
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if __name__=="__main__":
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print "Fruit price:%d"%Fruit.price
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apple = Fruit()
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print "apple price:%d"%apple.price
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banane = Fruit()
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print "banane price:%d"%banane.price
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apple.price=30
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Fruit.price=50
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print "apple price:%d"%apple.price
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print "banane price:%d"%banane.price
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#结果
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Fruit price:0
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apple price:0
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banane price:0
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apple price:30
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banane price:50
如果实例修改了类属性就会脱离类属性。
类的方法
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class Fruit:
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price = 0
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def __init__(self):
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self.color='red'
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zone="china"
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def printColor(self):
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print "color:"+self.color
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def printPrice(self):
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print "price:%d"%self.price
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@staticmethod
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def printStatic():
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print "static"
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if __name__=="__main__":
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Fruit.printStatic()
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apple = Fruit()
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apple.printStatic()
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apple.printPrice()
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apple.printColor()
普通方法自带self参数，可以通过self访问实例属性和类属性。而静态方法不自带self参数，也不能通过self访问实例参数和类参数。
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class Fruit:
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price = 0
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@staticmethod
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def printStatic():
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print Fruit.price
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if __name__=="__main__":
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Fruit.printStatic()
它只能通过类直接访问。
构造函数和析构函数
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class Fruit:
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count=0
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def __init__(self):
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print "我被调用了"
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def __del__(self):
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print "我也不幸被调用了"
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if __name__=="__main__":
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apple = Fruit()
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#结果
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我被调用了
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我也不幸被调用了
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class Fruit:
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count=0
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def __init__(self):
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print "我被调用了"
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def __del__(self):
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print "我也不幸被调用了"
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if __name__=="__main__":
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apple = Fruit()
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Fruit.count
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#结果
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我被调用了
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我也不幸被调用了
还类初始化和销毁的时候被调用。
而类被调用的时候不会被自动调用。
总结
这次对类做了一些基本的介绍。下一次我们谈谈继承、多态。
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