Question

如何防止python对象添加变量

class baseClass1:
    count=0;
    def displayCount(self):
        print "Total Employee %d" % baseClass1.count;


base = baseClass1();
base.type = "class"; #  i want to throw an error here

Answer 1

您可以使用__slots__ - 查看the documentation。

class baseClass1(object):
    __slots__ = ['count']

未知属性抛出的异常将是AttributeError。

你必须确保使用新式的类来实现（显式继承自object）

Answer 2

您可以覆盖班级“__setattr__并执行您想要的任何检查。在这个例子中，我不允许和设置未在构造函数中定义的成员。它将使您免于手动维护该列表。

class baseClass1:
        # allowed field names
        _allowed = set()

        def __init__(self): 
            # init stuff
            self.count=0
            self.bar = 3

            # now we "freeze the object" - no more setattrs allowed
            self._frozen = True

        def displayCount(self):

            print "Total Employee %d" % baseClass1.count;



        def __setattr__(self, name, value):

            # after the object is "frozen" we only allow setting on allowed field
            if  getattr(self, '_frozen', False) and name not in self.__class__._allowed:
                raise RuntimeError("Value %s not allowed" % name)
            else:
                # we add the field name to the allowed fields
                self.__class__._allowed.add(name)
                self.__dict__[name] = value



    base = baseClass1();
    base.count = 3 #won't raise
    base.bar = 2 #won't raise
    base.type = "class"; # throws

阻止python对象添加变量

2 个答案: