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How do I save and restore multiple variables in python? Ask Question

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How do I save and restore multiple variables in python? Ask Question

I need to save about a dozen objects to a file and then restore them later. I've tried to use a for loop with pickle and shelve but it didn't work right.

Edit.
All of the objects that I was trying to save were in the same class (I should have mentioned this before), and I didn't realize that I could just save the whole class like this:

import pickle
def saveLoad(opt):
    global calc
    if opt == "save":
        f = file(filename, 'wb')
        pickle.dump(calc, f, 2)
        f.close
        print 'data saved'
    elif opt == "load":
        f = file(filename, 'rb')
        calc = pickle.load(f)
    else:
        print 'Invalid saveLoad option'

ベストアンサー1

If you need to save multiple objects, you can simply put them in a single list, or tuple, for instance:

import pickle

# obj0, obj1, obj2 are created here...

# Saving the objects:
with open('objs.pkl', 'w') as f:  # Python 3: open(..., 'wb')
    pickle.dump([obj0, obj1, obj2], f)

# Getting back the objects:
with open('objs.pkl') as f:  # Python 3: open(..., 'rb')
    obj0, obj1, obj2 = pickle.load(f)

If you have a lot of data, you can reduce the file size by passing protocol=-1 to dump(); pickle will then use the best available protocol instead of the default historical (and more backward-compatible) protocol. In this case, the file must be opened in binary mode (wb and rb, respectively).

The binary mode should also be used with Python 3, as its default protocol produces binary (i.e. non-text) data (writing mode 'wb' and reading mode 'rb').

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