Pickle __getstate__ __setstate__ and restoring n/w - beazley pg 172
Veek. M
vek.m1234 at gmail.com
Wed Mar 9 04:14:36 EST 2016
dieter wrote:
> "Veek. M" <vek.m1234 at gmail.com> writes:
>
>> import socket
>> class Client(object):
>> def __init__(self,addr):
>> self.server_addr = addr
>> self.sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
>> self.sock.connect(addr)
>>
>> def __getstate__(self):
>> return self.server_addr
>>
>> def __setstate__(self,value):
>> self.server_addr = value
>> self.sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
>> self.sock.connect(self.server_addr)
>> -----------------
>>
>> We'd use it like so:
>> x = Client(192.168.0.1)
>> import pickle
>> pickle.dump(x) #getstate gets called and returns IP for pickling.
>>
>> #program exits, we restart it
>> x=Client(None)
>> x = pickle.load(fh) #Is the IP passed to setstate??????
>> x.__setstate__(self, unpickledIP) ???
>> Is this correct?
>
> Not completely.
>
> "pickle" operates on objects - and calls "__getstate__" and
> "__setstate__" internally. Thus, you get something like:
>
> client = Client()
> pickle.dump(client, open(fn, "wb"))
> ....
> recreated_client = pickle.load(open(fn, "rb"))
hmm.. yeah, as in the fh - file handle will be passed for
pickling/unpickling - that's not important..
what i wanted to know was, x = Client('192.168.0.1') will create an
object 'x' with the IP inside it. When I do:
pickle.dump(x)
pickle doesn't know where in the object the IP is, so he'll call
__getstate__ and expect the return value to be the IP, right?
Similarly, whilst unpickling, __setstate__ will be called in a manner
similar to this:
x.__setstate__(self, unpickledIP)
__setstate__ can then populate 'x' by doing
self.x = str(unpickledIP)
the type info is not lost during pickling is it, therefore 'str' is not
required is it?
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