Pickle a list

[Chris Kaynor]

Chris


2011/3/7 Rogério Luz <rogeriosantosluz at gmail.com>

> Chris, Thanks a lot for your explanation, I got it
>
> class MyClass:
>     #class variables
>
>     teste = 0
>     nome = None
>     lista = ["default"]
>
>     def __init__(self):
>         #instance variables
>         self.lista = MyClass.lista #  if I still want "default" class
> variable
>
>         for reg in range(1,10):
>             self.lista.append(reg)
>         self.nome = "Teste"
>         self.teste = 19900909


While this will work, keep in mind that all instances of MyClass will share
the same list.

# Untested
>> a = MyClass()
>> print a.lista
['default', 1, 2, 3, 4, 5, 6, 7, 8, 9]
>> a = MyClass()
>> print a.lista
['default', 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9]


To get around this, you'd need to copy the list (see the copy module).


>
> On Mon, Mar 7, 2011 at 1:51 PM, Chris Kaynor <ckaynor at zindagigames.com>wrote:
>
>> On Mon, Mar 7, 2011 at 8:38 AM, Rogerio Luz <rogeriosantosluz at gmail.com>wrote:
>>
>>> Hi All
>>>
>>> I'd like to pickle an object instance with all values. So I
>>> instanciate myClass and set some values including a list with more
>>> values (in the __init__), then dump to file. I realized that the
>>> pickled object don't saved my new list values (saved only the
>>> "default" value) but saved a String and an int. What I'm doing wrong?
>>> Thanks Rogerio
>>>
>>> $ python3 pickler.py P
>>> Dump: ['default', 1, 2, 3, 4, 5, 6, 7, 8, 9] TestStr 19900909
>>>
>>> $ python3 pickler.py U
>>> Load: ['default'] TestStr 19900909
>>>
>>> # pickler.py
>>>
>>> import sys
>>> import pickle
>>>
>>> class MyClass:
>>>    teste = 0
>>>    nome = None
>>>    lista = ["default"]
>>>
>>>    def __init__(self):
>>>        for reg in range(1,10):
>>>            self.lista.append(reg)
>>>        self.nome = "TestStr"
>>>        self.teste = 19900909
>>>
>>
>> In this definition, you are creating a class variable then appending your
>> arguments to it. Pickling won't save class variables - only
>> instance variables. The string and int work as you are reassigning them
>> within the __init__ function, thereby making them instance variables.
>>
>> Something like:
>>
>> class MyClass:
>>    teste = 0
>>    nome = None
>>
>>    def __init__(self):
>>         self.lista = ['default']
>>        for reg in range(1,10):
>>            self.lista.append(reg)
>>        self.nome = "TestStr"
>>        self.teste = 19900909
>>
>>
>>
>>> #main
>>> def main(argv):
>>>    if argv[1] == "P":
>>>        with open('myClass.pickle', 'wb') as f:
>>>            myClass = MyClass()
>>>            print("Dump:",myClass.lista, myClass.nome, myClass.teste)
>>>            pickle.dump(myClass, f, pickle.HIGHEST_PROTOCOL)
>>>
>>>    elif argv[1] == "U":
>>>        with open('myClass.pickle', 'rb') as f:
>>>            myClass = pickle.load(f)
>>>            print("Load:",myClass.lista, myClass.nome, myClass.teste)
>>>
>>> if __name__ == "__main__":
>>>    main(sys.argv)
>>> --
>>> http://mail.python.org/mailman/listinfo/python-list
>>>
>>
>>
>
>
> --
> []´s
>
> Rogério Luz
>
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