comb_num

def comb_num(size):
    '''Accept a digit and return a list of lists of digits between 0 and
    that digit including 0, selected 1 at a time, 2 digits at a time,...
    up till the position of the specified digit.

    For example the function accepts a digit 3 and returns a list of lists:
    [[0], [1], [2], [0, 1], [0, 2], [1, 2], [0, 1, 2]]
    '''
    finalresult = []
    def comb_num_norep(size, numdigits):
        supresult = {}
        def comb_num_rep(size, numdigits):
            if numdigits == 1: result = ([elements] for elements in range(size))
            else:
                result = (element2 + [element3] for element2 in \
                comb_num_rep(size, numdigits - 1) for element3 in range(size) \
                if element3 not in element2)
            return result
        for elements in comb_num_rep(size, numdigits):
            elements.sort()
            keytuple = tuple(elements)
            try:
                supresult[keytuple] += 1
            except KeyError:
                supresult[keytuple] = 1
        return [list(element) for element in list(supresult)]
    for numdigits in range(1, size + 1):
        finalresult += comb_num_norep(size, numdigits)
    return finalresult