Re: Pickling an instance of a class containing a dict doesn't work
Peter Otten wrote: Chances are you have inadvertently created an /instance/ attribute build_steps which was then saved: s = subproject() # ... s.configuration[name] = my dinner # modifies the class attribute s.build_steps = [hunt, kill, cook] # creates an instance attribute Yes, now I see. That's the way I filled the dict and the list. Thank you for the explanation :) Marco -- http://mail.python.org/mailman/listinfo/python-list
Pickling an instance of a class containing a dict doesn't work
Hello there,
I want to save an instance of a class containing a dictionary with the
pickle-module.
The class looks like this:
class subproject:
configuration = {}
build_steps = []
# some functions
# ...
Now I create an instance of this class, e.g.
test = subproject()
and try to save it with pickle.dump(test, file('test.pickle','wb')) or with
pickle.Pickler(file('test.pickle','wb')).save(test) it looks like
everything has worked well, but in the saved file 'test.pickle' only the
list 'build_steps' is saved - the dictionary 'configuration' is missing.
There is wether an error-message nor an exception.
When I try to save only the dictionary, there is no problem at all - the
dict is saved to the file.
I also tried the 3 different protocols (0, 1, 2), but none of them worked
for me.
I hope somebody knows what to do ;)
Thanks for reading
Marco
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Re: Pickling an instance of a class containing a dict doesn't work
Marco Lierfeld wrote:
The class looks like this:
class subproject:
configuration = {}
build_steps = []
# some functions
# ...
Now I create an instance of this class, e.g.
test = subproject()
and try to save it with pickle.dump(test, file('test.pickle','wb')) or with
pickle.Pickler(file('test.pickle','wb')).save(test) it looks like
everything has worked well, but in the saved file 'test.pickle' only the
list 'build_steps' is saved - the dictionary 'configuration' is missing.
There is wether an error-message nor an exception.
When I try to save only the dictionary, there is no problem at all - the
dict is saved to the file.
I also tried the 3 different protocols (0, 1, 2), but none of them worked
for me.
At a wild guess. Since pickle descends the objects hierarchy, and since
configuration and build_steps aren't local to an instance of a class,
it stores only a reference to them (so you won't see values). However,
if you change the above to:
class subproject:
def __init__(self):
configuration = { }
build_steps = [ ]
That'll probably be what you expect...
Jon.
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Re: Pickling an instance of a class containing a dict doesn't work
Jon Clements wrote:
if you change the above to:
class subproject:
def __init__(self):
configuration = { }
build_steps = [ ]
Of course, I actually meant to write self.configuration and
self.build_steps; d0h!
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Re: Pickling an instance of a class containing a dict doesn't work
Marco Lierfeld [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
Hello there,
I want to save an instance of a class containing a dictionary with the
pickle-module.
The class looks like this:
class subproject:
configuration = {}
build_steps = []
# some functions
# ...
Now I create an instance of this class, e.g.
test = subproject()
and try to save it with pickle.dump(test, file('test.pickle','wb')) or
with
pickle.Pickler(file('test.pickle','wb')).save(test)
I'm guessing that configuration and build_steps are supposed to be instance
variables, not class-level variables. It would be interesting to see what
your __init__ method looks like. I'm guessing you assign something the
self.build_steps in __init__, but self.configuration is omitted.
Try moving these initializers into the __init__ method, as:
class subproject:
def __init__(self):
self.configuration = {}
self.build_steps = []
and see if pickle starts behaving better.
-- Paul
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Re: Pickling an instance of a class containing a dict doesn't work
Jon Clements wrote:
if you change the above to:
class subproject:
def __init__(self):
configuration = { }
build_steps = [ ]
Of course, I actually meant to write self.configuration and
self.build_steps; d0h!
Thank you Jon and Paul, you both were 100% right :)
But I still don't understand, why the list was saved and the dict was not...
confusing ;)
Bye,
Marco
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Re: Pickling an instance of a class containing a dict doesn't work
Marco Lierfeld wrote:
Jon Clements wrote:
if you change the above to:
class subproject:
def __init__(self):
configuration = { }
build_steps = [ ]
Of course, I actually meant to write self.configuration and
self.build_steps; d0h!
Thank you Jon and Paul, you both were 100% right :)
But I still don't understand, why the list was saved and the dict was
not... confusing ;)
Chances are you have inadvertently created an /instance/ attribute
build_steps which was then saved:
s = subproject()
# ...
s.configuration[name] = my dinner # modifies the class attribute
s.build_steps = [hunt, kill, cook] # creates an instance attribute
Peter
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