Pickle, __init__, and classes

[Yin]

I've created a class that reads in and processes a file in the
initializer __init__. The processing is fairly substantial, and thus,
instead of processing the file every time the object is created, I
pickle the object to a file.

In subsequent creations of the object, I implement a test to see
whether the pickled file exists. If it does, then I unpickle the
object.

Unfortunately, the __init__ cannot return this unpickled object.

I've used an auxiliary member function which fixes the problem, but I
would prefer to have the correct object returned at instantiation
rather than returned from the auxiliary member function.

Are there other ways of approaching this problem?

Thanks,
Yin

[Russell Blau]

"Yin" <yi*******@yahoo.com> wrote in message
news:11**********************@g47g2000cwa.googlegr oups.com...

I've created a class that reads in and processes a file in the
initializer __init__. The processing is fairly substantial, and thus,
instead of processing the file every time the object is created, I
pickle the object to a file.

In subsequent creations of the object, I implement a test to see
whether the pickled file exists. If it does, then I unpickle the
object.

Unfortunately, the __init__ cannot return this unpickled object.

Try __new__(). http://docs.python.org/ref/customization.html This isn't
the usual application of __new__, but since it returns an object it should
be ideal for your purposes.

[Peter Hansen]

Russell Blau wrote:

Try __new__(). http://docs.python.org/ref/customization.html This isn't
the usual application of __new__, but since it returns an object it should
be ideal for your purposes.

Or simply create a factory function to return your instances -- which is
in effect what __new__ does -- but without the baggage.

-Peter