如何使用'pickle‘

Question

我的代码(我无法使用'pickle')：

class A(object):
    def __getstate__(self):
        print 'www'
        return 'sss'
    def __setstate__(self,d):
        print 'aaaa'

import pickle
a = A()
s = pickle.dumps(a)
e = pickle.loads(s)
print s,e

打印：

www
aaaa
ccopy_reg
_reconstructor
p0
(c__main__
A
p1
c__builtin__
object
p2
Ntp3
Rp4
S'sss'
p5
b. <__main__.A object at 0x00B08CF0>

谁能告诉我如何使用。

Answer 1

你想做什么？它对我来说很有效：

class A(object):
    def __init__(self):
        self.val = 100

    def __str__(self):
        """What a looks like if your print it"""
        return 'A:'+str(self.val)

import pickle
a = A()
a_pickled = pickle.dumps(a)
a.val = 200
a2 = pickle.loads(a_pickled)
print 'the original a'
print a
print # newline
print 'a2 - a clone of a before we changed the value'
print a2
print 

print 'Why are you trying to use __setstate__, not __init__?'
print

所以这将打印出来：

the original a
A:200

a2 - a clone of a before we changed the value
A:100

如果您需要setstate：

class B(object):
    def __init__(self):
        print 'Perhaps __init__ must not happen twice?'
        print
        self.val = 100

    def __str__(self):
        """What a looks like if your print it"""
        return 'B:'+str(self.val)

    def __getstate__(self):
        return self.val

    def __setstate__(self,val):
        self.val = val

b = B()
b_pickled = pickle.dumps(b)
b.val = 200
b2 = pickle.loads(b_pickled)
print 'the original b'
print b
print # newline
print 'b2 - b clone of b before we changed the value'
print b2

打印的内容：

Why are you trying to use __setstate__, not __init__?

Perhaps __init__ must not happen twice?

the original b
B:200

b2 - b clone of b before we changed the value
B:100

Answer 2

你可以使用pickle (意思是，这段代码可以正常工作)。你似乎只是得到了一个结果，你并不期望。如果您希望得到相同的“输出”，请尝试：

import pickle
a = A()
s = pickle.dumps(a)
e = pickle.loads(s)
print s, pickle.dumps(e)

你的例子并不是一个典型的‘酸洗’例子。通常，酸洗过的对象被持久地保存在某个地方，或者通过网络发送。例如，参见pickletest.py：http://www.sthurlow.com/python/lesson10/。

pickling有一些高级用法，例如，请参阅David Mertz XML对象序列化文章：http://www.ibm.com/developerworks/xml/library/x-matters11.html

Answer 3

简而言之，在您的示例中，e等于a。

不必关心这些strang字符串，你可以转储这些字符串以保存到任何地方，只要记住当你加载它们时，你又得到了'a‘对象。