Pickle：同时使用\uugestate和\uugetnewargs__

Question

我在Python2.7上使用pickle。我试图调用我重写的__getstate__和{}两个方法。我不能pickle属性c，因为它是类D的一个实例。在

 nn = C(7, 2)
 nn.d = 1
 pickle.dump(nn, open('c_save.p', 'wb'))
 nn2 = pickle.load(open('c_save.p', 'rb'))
 print nn2.__dict__

退货：

^{pr2}$

我看不到应该创建属性c的__getnewargs__调用。在

我的代码：

import pickle

class D(object):
    def __init__(self, i, j):
        self.i = i
        self.j = j

class C(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b
        self.c = D(a, b)
        self.d = 0

    def __getstate__(self):
        print 'getstate was called'
        odict = self.__dict__.copy()
        del odict['c']
        return odict

    def __getnewargs__(self):
        print 'getnewargs was called'
        return (self.b,self.a)

    def __setstate__(self, dict):
        print 'setstate was called'
        self.__dict__.update(dict)

Answer 1

从docs：

New-style types can provide a getnewargs() method that is used for protocol 2.

对于^{}：

If the protocol parameter is omitted, protocol 0 is used.

因此，协议2必须明确设置为：

pickle.dump(nn, open('c_save.p', 'wb'), protocol=2)