[Jython-users] Issue with None and Serialization

[chuck c. <cc...@zi...>]

I'm using Jython for my project and today we tried adding the
functionality where you can save out a Config object and then when you
restart you can load a Config if you need it.  I'm using the java.io
libraries to do this because I can't assume pickle or any of the other
python libraries are on the machine.

However I ran into an issue where after reading the serialized object in
some statements which checked to see if an attribute on the object is
None were failing.  I've recreated the problem in the code snippet below
as succinctly as I can.  Does anyone have any ideas on what I'm doing
wrong?  I have a feeling it must be something really simple or could
this be a bug in Jython?

TIA
chuck

-------code-------
from java.io import *
from org.python.util import *

class Test(Serializable):
    def __init__(self):
        self.attr = None
    def test(self):
        print "attr is None:", self.attr is None
        print "attr type is:", type(self.attr)
        print "attr == None:", self.attr == None

def load(path):
    file = File(path)
    fileIn = FileInputStream(file)
    pyIn = PythonObjectInputStream(fileIn)
    pyObj = pyIn.readObject()
    pyIn.close()
    return pyObj

def save(obj, path):
    fileOut = FileOutputStream(path)
    objOut = ObjectOutputStream(fileOut)
    objOut.writeObject(obj)
    objOut.flush()
    objOut.close()

print "Testing initial object..."
a = Test()
a.test()
save(a, "test.out")
b = load("test.out")
print "Testing deserialized object..."
b.test()

-----results----
Testing initial object...
attr is None: 1
attr type is: org.python.core.PyNone
attr == None: 1
Testing deserialized object...
attr is None: 0
attr type is: org.python.core.PyNone
attr == None: 0

I would expect that if the attribute is of Type PyNone then it should
return 1 to
attr is None
and
attr == None

I thought the problem might be that between serializing/deserializing I
might somehow be getting a different instance of PyNone but this isn't
the case as evidenced below when I inspect the objects in the
interpreter after running th code above
>>> type(a.attr)
<jclass org.python.core.PyNone at 334527779>
>>> type(b.attr)
<jclass org.python.core.PyNone at 334527779>