myStore: python persistence.

class myStore:
    # The store saves to self.fn, and drops a copy in self.fn+version.  This is the version
    # control.  So always load from the current version using the default filename.  It also
    # contains the current version number so no need for filename antics.  All results are 
    # kept in the local `res` directory so store functions ultimately load and save the `res`
    # dict.
    # Use as,
    # res = myStore() # instantiate, get latest version
    # r = res.res # shorthand.  Refer to r[] as result dict.
    # r['testValue'] = 1 # set dict value/
    # res.update() # Writes to disk and updates version.

    # del(r); del(res)
    # res = myStore() # instantiate, get latest version and data.
    # r = res.res
    # r['testValue'] # works.

    import os, pickle, cPickle

    def restore(self):
        """Opens the store file, pulls everything from it.  Run this at instanciation only."""
        with file(self.root + self.filename, 'r') as a:
            self.res = self.cPickle.load(a)
            self.version = self.cPickle.load(a)
            print 'Loaded data from store v%i' % (self.version)

    def __init__(self, filename = ''):
        self.root = '/home/starnesm/projects/FT/ipython/'

        # if a filename given, use it to name the store.  Otherwise, use default.
        if filename == '':
            self.filename = 'carAndBikeImpedanceMeasurementsData.pickle'
        else:
            self.filename = filename

        self.res = dict() # default values
        self.version = 1 # to be replaced if store exists:

        if (self.filename) in self.os.listdir(self.root):
            # the store exists.  Load it and get version number.
            with file(self.root + self.filename, 'r') as a:
                self.res = self.pickle.load(a)
                self.version = self.pickle.load(a)

        print 'myStore is at version ', self.version

    def update(self):
        """Opens the store file, pickles the thing and puts it in it."""
        self.version += 1
        with file(self.root + self.filename, 'w') as a:
            self.pickle.dump(self.res, a)
            self.pickle.dump(self.version, a)
        with file(self.root + self.filename + '.' + str(self.version), 'w') as a:
            self.pickle.dump(self.res, a)
            self.pickle.dump(self.version, a)

        print 'Version updated to v', self.version