jkn wrote:
> Hi Peter
>
> On Apr 3, 8:54 am, Peter Otten <__pete...@web.de> wrote:
>> jkn wrote:
>> > I'm clearly not understanding the 'can't pickle instancemethod
>> > objects' error; can someone help me to understand,
>>
>> I think classes implemented in C need some extra work to make them
>> picklable, and that hasn't been done for instance methods.
>
> by 'classes implemented in C', doyou mean new-style classes', or what,
> please?
Given
>>> class A(object):
... def __init__(self, name):
... self.name = name
... def hello(self):
... print "Hello,", self.name
...
>>> a = A("Peter")
>>> hello = a.hello
>>> hello()
Hello, Peter
the object bound to the name 'hello' is an instance of the 'instancemethod'
type:
>>> type(hello)
<type 'instancemethod'>
That type is implemented in C, see
http://hg.python.org/cpython/file/9599f091faa6/Objects/classobject.c
and doesn't support the pickle protocol while a similar class,
functools.partial which is also written in C, see
http://hg.python.org/cpython/file/9599f091faa6/Modules/_functoolsmodule.c
does:
>>> from functools import partial
>>> import pickle
>>> def hello(obj):
... print "Hi,", obj.name
...
>>> hello2 = partial(hello, a)
>>> hello2()
Hi, Peter
>>> s = pickle.dumps(hello2)
>>> pickle.loads(s)()
Hi, Peter
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