stored_result(): automatic serialization of expensive calculations

A very common situation I encounter: "Do [expensive calculation] and pickle the result; unless it's been done before, in which case unpickle the stored result." This stored_result() utility function makes that very easy, and provides some convenient options for scripting and memory management."

def stored_results(pkl_filename, function, overwrite=0, verbose=1,
          lazy=False, args=[], kwargs={}):
    """Returns contents of pickled file 'pkl_filename'.  If file does not exist
    or is malformed, returns output of function (with args & kwargs) and pickles same
    result to pkl_filename.
    If overwrite>0, runs function regardless of presence of 'pkl_filename'.
    If lazy=True, instead outputs a generator that evaluates the rest of the stored_results()
    call only when its next() method is called."""
    import cPickle
    if lazy:
        # Create a generator that will eventually retrieve stored result
        def result_gen():
            result = stored_results(pkl_filename, function, overwrite, verbose,
                                    False, args, kwargs)
            while 1:
                yield result
        return result_gen()
    else:
        if not overwrite>0:
            try:
                inf = file(pkl_filename, 'rb')
                result = cPickle.load(inf)
                inf.close()
                if verbose: print pkl_filename, "successfully unpickled"
                return result
            except (cPickle.UnpicklingError, IOError):
                if verbose: print "Result not stored.  Running function", function.func_name
        result = function(*args, **kwargs)
        outf = file(pkl_filename, 'wb')
        cPickle.dump(result, outf, -1)
        outf.close()
        if verbose: print "Result pickled to", pkl_filename
        return result

Typical use:
result = stored_results('saved_result.pkl', expensive_function, args=(23, 'sweet'))

Advanced use:
To perform the calculation/load the result in a just-in-time fashion:
result_gen = stored_results('saved_result.pkl', expensive_function, args=(23, 'sweet'), lazy=True)
[memory-sensitive tasks that may or may not need the result]
result = result_gen.next()