Hello everyone,
I am trying to serialize a function, class, etc and transfer it, have it
unserialized and used. The thing is that this code is not defined on the
receiving side and thus it does not work. I tried the following tests:
Terminal A:
>>> import pickle
>>> def test(): pass
...
>>> pickle.dumps(test)
'c__main__\ntest\np0\n.'
>>>
Terminal B:
>>> import pickle
>>> pickle.loads('c__main__\ntest\np0\n.')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.5/pickle.py", line 1374, in loads
return Unpickler(file).load()
File "/usr/lib/python2.5/pickle.py", line 858, in load
dispatch[key](self)
File "/usr/lib/python2.5/pickle.py", line 1090, in load_global
klass = self.find_class(module, name)
File "/usr/lib/python2.5/pickle.py", line 1126, in find_class
klass = getattr(mod, name)
AttributeError: 'module' object has no attribute 'test'
Ok, so pickle needs the code to be defined on both sides, so I tried
marshal:
Terminal A:
>>> import marshal
>>> marshal.dumps(test)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: unmarshallable object
Ok, as the docs say, marshal is quite limited, no functions or user
classes can be marshalled, I did get it to work like this though :
>>> import inspect
>>> marshal.dumps(inspect.getmembers(test, inspect.iscode)[0][1])
'c\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00C\x00\x00\x00s\x04\x00\x00\x00d\x00\x00S(\x01\x00\x00\x00N(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00s\x07\x00\x00\x00<stdin>t\x04\x00\x00\x00test\x01\x00\x00\x00s\x00\x00\x00\x00'
ok, but can I unmarshal it?
Terminal B:
>>>
marshal.loads('c\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00C\x00\x00\x00s\x04\x00\x00\x00d\x00\x00S(\x01\x00\x00\x00N(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00s\x07\x00\x00\x00<stdin>t\x04\x00\x00\x00test\x01\x00\x00\x00s\x00\x00\x00\x00')
<code object test at 0xb7591578, file "<stdin>", line 1>
ok, it seams to work...
>>>
marshal.loads('c\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00C\x00\x00\x00s\x04\x00\x00\x00d\x00\x00S(\x01\x00\x00\x00N(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00s\x07\x00\x00\x00<stdin>t\x04\x00\x00\x00test\x01\x00\x00\x00s\x00\x00\x00\x00')()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'code' object is not callable
ok, logical, it's a code object...
>>>
eval(marshal.loads('c\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00C\x00\x00\x00s\x04\x00\x00\x00d\x00\x00S(\x01\x00\x00\x00N(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00(\x00\x00\x00\x00s\x07\x00\x00\x00<stdin>t\x04\x00\x00\x00test\x01\x00\x00\x00s\x00\x00\x00\x00'))
ok, this works, not super pretty, but it works
now user objects?
>>> class A(object): pass
...
>>> a = A()
>>> marshal.dumps(a)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: unmarshallable object
ok, expected...
>>> inspect.getmembers(a, inspect.iscode)
[]
ok, not cool, can't use the previous method...
Ok, now a word about what I'm trying to do, I'm trying to run python
code in a new process, like multiprocessing does, but without
multiprocessing. I'm trying to serialise the code because I 'd like to
do something like:
pseudo-code, serialize/unserialize/process are made up:
def newProcess(func, *args, **kwargs):
func = serialize(func)
args = serialize(args)
kwargs = serialize(kwargs)
process("python -c 'import serialize, unserialize;print
serialize(unserialize(\'%s\')(*unserialize(\'%s\'),
**unserialize(\'%s\')))'" % (func, args, kwargs))
#read result from stdout
I'm greatly simplifying this because I'm using a framework, but that's
the basic idea.
thanks,
Gabriel
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