Python - 如何从属性类中获取类实例引用？

Question

class A()  
    att = B()  

class B()  
    ... 

a = A() 

b = B() 

a.att = b 

b怎样才能得到一个参考？我需要获得这里的属性。

谢谢！

Answer 1

您可以制作一个通用的“Reference（）”类，它在属性词典中保留对其自身的任何引用。

class Reference(object): 
    def __init__(self): 
     self.references = {} 

    def __setattr__(self, key, value): 
     if hasattr(self, 'references'): 
      if isinstance(value, Reference): 
       if not key in value.references: 
        value.references[key] = [] 
       value.references[key].append(self) 

      elif value is None and hasattr(self, key): 
       old = getattr(self, key).references 
       if key in old and self in old[key]: 
        old[key].remove(self) 

     super(Reference, self).__setattr__(key, value) 

，然后创建类：

class A(Reference): 
    def __init__(self): 
     super(A, self).__init__() 
     self.att = None 

class B(Reference): 
    def __init__(self): 
     super(B, self).__init__() 
     self.att = None 

并使用它：

a = A() 
b = B() 

print 'A references', a.references 
print 'B references', b.references 
# A references {} 
# B references {} 

a.att = b 

print 'A references', a.references 
print 'B references', b.references 
# A references {} 
# B references {'att': [<__main__.A object at 0x7f731c8fc910>]} 

最后，你必须从任何性能

反向引用的所有参考类

Answer 2

最简单的方法是在B中需要A的方法中添加一个额外的函数参数，并在调用时传递它。或者，只是让B的初始化拿一个A作为参数，包括和改变的init将该位ATT = B（个体经营）

Answer 3

class A(object): 
    def __init__(self): 
     self.att = B(self) 

class B(object): 
    def __init__(self, a): 
     self.a = a 

a = A() 

a.att.a is a 

或另一种方式，

class A(object): 
    def __init__(self, b): 
     b.a = self 
     self.att = b 

class B(object): 
    pass 

a = A(B()) 

a.att.a is a 

Answer 4

此代码没有按没有多大意义......但如果我正确理解你的问题......

class A(object): 
    pass  #or whatever you like 

class B(object): 
    def __init__(self, ref): #accept one argument 
     self.ref = ref 

a = A() 

b = B(a) #pass `a` as that argument 

a.att = b 

可能是一个答案。

Answer 5

class A(object): 

    def __init__(self): 
     self._att=None 

    @property 
    def att(self): 
     return self._att 

    @att.setter 
    def att(self, value): 
     self._att = value 
     value.parent = self 


class B(object): 

    pass 

a = A() 

b = B() 

a.att = b 
print b.parent