1.1 访问控制
1.1.1 外部代码修改实例的属性
>>> daidai = Student(‘DAIDAI‘, 99)
>>> daidai.score
99
>>> daidai.score = 99 + 1 --修改score属性
>>> daidai.score
100
1.1.2 外部代码访问实例属性限制
>>> class Student(object):
... def __init__(self, name,score):
... self.__name = name
... self.__score = score
... def print_score(self):
... print(‘%s: %s‘ % (self.__name, self.__score))
...
>>> daidai = Student(‘DAIDAI‘, 99)
>>> daidai.__name
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: ‘Student‘ object has noattribute ‘__name‘
在Python中，实例的变量名如果以__开头，就变成了一个私有变量（private），只有内部可以访问，外部不能访问。当然，此时外部代码肯定不能修改内部实例的属性。
此时修改属性变量需调用方法
>>> class Student(object):
... def __init__(self, name,score):
... self.__name = name
... self.__score = score
... def set_name(self, name):
... self.__name = name
... def set_score(self, score):
... self.__score = score
... def print_score(self):
... print(‘%s: %s‘ % (self.__name, self.__score))
...
>>>
>>>
>>> daidai = Student(‘DAIDAI‘, 99)
>>> daidai.print_score()
DAIDAI: 99
>>> daidai.set_name(‘xiongxiong‘)
>>> daidai.print_score()
xiongxiong: 99
获取实例的变量属性需通过方法
class Student(object):
...
def get_name(self):
return self.__name
def get_score(self):
return self.__score
调用方法修改变量属性时，参数检查
>>> class Student(object):
... def __init__(self, name,score):
... self.__name = name
... self.__score = score
... def set_name(self, name):
... self.__name = name
... def set_score(self, score):
... if 0 <= score <= 100: --参数检查控制部分
... self.__score = score
... else:
... raise ValueError(‘bad score‘)
... def print_score(self):
... print(‘%s: %s‘ % (self.__name, self.__score))
...
>>>
>>> daidai = Student(‘DAIDAI‘, 99)
>>> daidai.print_score()
DAIDAI: 99
>>> daidai.set_score(-1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 11, in set_score
ValueError: bad score
注意：
__xxx__ 特殊变量，可以访问
__xxx 私有变量，不可访问
_xxx 可以访问，不推荐这样写
>>> class Student(object):
... def __init__(self, name,score):
... self._name = name
... self._score = score
... def set_name(self, name):
... self.__name = name
... def set_score(self, score):
... if 0 <= score <= 100:
... self.__score = score
... else:
... raise ValueError(‘bad score‘)
... def print_score(self):
... print(‘%s: %s‘ % (self.__name, self.__score))
...
>>>
>>>
>>> daidai = Student(‘DAIDAI‘, 99)
>>> daidai._name
‘DAIDAI‘