pickle error when called in class

Question

I'm trying to put a method in one of my classes which will allow me to pickle and unpickle files. So for example, I have

import pickle

class SomeClass:

    def otherMethods:
        pass

    def save_to_file(self, filename, file_to_save):
        with (filename,'wb') as output:
            pickle.dump(file_to_save,output,pickle.HIGHEST_PROTOCOL)
        print("Data has been saved.")

Now, when I create an instance of this 'SomeClass', I expect to be able to call as follows from the terminal...

myfile = [1,2,3] # or anything else
SomeClass.save_to_file('myfile.pk',myfile)

However, what gets thrown is an:

'AttributeError: __exit__'

I've seen a few different posts of people having difficulties with similar use cases, but I haven't been able to figure out how they apply in my situation. Help would be much appreciated.

did you call SomeClass.save_to_file or SomeClassObj.save_to_file? — Marcus
– Marcus, Commented Jun 7, 2013 at 5:22
I created an instance of SomeClass... i.e a = SomeClass(), then a.save_to_file(...) — Flaminator
– Flaminator, Commented Jun 7, 2013 at 5:23

Janne Karila · Accepted Answer · 2013-06-07 05:26:51Z

11

open is missing:

with open(filename,'wb') as output:

The with statement expects a context manager with __enter__ and __exit__ methods, and raises AttributeError because the tuple (filename,'wb') does not have them.

answered Jun 7, 2013 at 5:26

Janne Karila

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