I have a class derived from string that is used in a pickle. In the new
version of my program, I moved the module containing the definition of the
class. Now the unpickle fails because it doesn't find the module. I was
thinking that I could make the unpickle work by putting a copy of the
module in the original location and then redefine the class by sticking a
__setstate__ in the class thusly:
def __setstate__(self, state):
self.__dict__.update(state)
self.__class__ = NewClassName
My plan was to specify the new location of the module in NewClassName.
However, when I do this I get the message "'class' object layout differs
from 'class'". I don't think that they do as the new module is a copy of
the old one. I suspect that I am not allowed to make the class assignment
because my class is derived from string. What is the best way to update
the pickle? The only thought I have is to read all the data with the old
class module, store the data in some nonpickle format, and then, with
another program, read the nonpickle-format file and rewrite the pickle with
the class module in the new location.
--
Jeffrey Barish
--
http://mail.python.org/mailman/listinfo/python-list
