如何將對象.__ dict__再次轉換爲對象本身？

Question

class Node(object): 
    def __init__(self, data): 
     self.data = data 

if __name__ == "__main__": 
    a = Node(5) 
    print a # prints __main__.Node object at 0x025C7530 
    print a.__dict__ # how can I turn this back into the previous line? 

反正有沒有把字典回到對象中？

Answer 1

對於某些類型的對象，你可以得到一個相同的對象（而不是對象本身，而是一個副本）：

class Node(object): 
    def __init__(self, data): 
     self.data = data 

if __name__ == "__main__": 
    a = Node(5) 
    a = a.__dict__ #whoops, now I lost the object, I just have the dict 
    b = Node.__new__(Node) # make a new empty object 
    b.__dict__ = a.copy() # copy in the dict 
    # copy because there might still a reference to the object elsewhere 
    # if you want changes to b to affect a, then don't copy just assign 
    print b.__dict__ 
    print b 

Answer 2

嚴格來說，你不能（沒有修改Node類）。 __dict__不保留對原始對象的引用。您可以通過複製字典有所建樹類似：

n1 = Node(5) 
n2 = Node.__new__(Node) # object created but not initiated. 
n2.__dict__ = n1.__dict__ 
n1.foo = 'something fooish' 

print n1.foo == n2.foo #True 

不幸的是，n1 != n2。

Answer 3

我只知道這是可能的老式類在Python 2：

class Ode(): # not derived from object 
    def __init__(self, data): 
     self.data = data 

>>> o = Ode(6) 
>>> o.data 
6 

>>> import new 
>>> od = o.__dict__ 
>>> od 
{'data': 6} 
>>> new.instance(Ode, od).data 
6 
>>> new.instance(Ode, {'data': 666}).data 
666 

但請注意，這不同於複製對象，我覺得你可能會遇到各種奇怪的問題（只提一個：對象的構造函數沒有被調用）。