Python通过属性手段实现只允许调用一次的示例讲解
如果希望一个对象的某个方法只能够调用一次,按照我之前的惯性思维,我肯定是定义一个状态量然后每次调用的时候修改它的值。通过查看状态量的数值,我可以决定采取执行不同的处理。
其实,除此之外还有一种方法,不仅仅能够实现这样的处理,还能够顺便处理对象的属性。
先看一下如下的代码:
class DemoClass: def __init__(self): pass def AttrCheck(self): try: self.value print("already hasvalue") raise ValueAttrError except AttributeError: self.value = 0 print(self.value) obj = DemoClass() obj.AttrCheck() obj.AttrCheck()
程序执行结果如下:
grey@DESKTOP-3T80NPQ:/mnt/e/01_workspace/02_programme_language/03_python/03_OOP/2017/08$python attr1.py 0 already has value Traceback (mostrecent call last): File "attr1.py", line 15, in<module> obj.AttrCheck() File "attr1.py", line 8, inAttrCheck raiseRuntimeError("multi-excued!") RuntimeError:multi-excued!
从上面的结果看,我们所描述到的功能已经这样实现了!
上面的属性是给了默认的赋值,我们当然也可以改成带有赋值数值的形式:
class DemoClass: def __init__(self): pass def AttrCheck(self,value): try: self.value print("already hasvalue") raiseRuntimeError("multi-excued!") except AttributeError: self.value = value print(self.value) obj = DemoClass() obj.AttrCheck(123) obj.AttrCheck(123)
程序的执行结果如下:
grey@DESKTOP-3T80NPQ:/mnt/e/01_workspace/02_programme_language/03_python/03_OOP/2017/08$python attr1.py 123 already has value Traceback (mostrecent call last): File "attr1.py", line 15, in<module> obj.AttrCheck(123) File "attr1.py", line 8, in AttrCheck raiseRuntimeError("multi-excued!") RuntimeError:multi-excued!
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