Python: converting list of lists to tuples of tuples

A Python newbie! I need help converting a list of lists tuples of tuples.

I want to call the append_as_tuples function, but every time I return it, it says
it can only concatenate lists (not tuples) to lists

Here is what I have so far:

def append_as_tuple(t, l):
    ''' Convert list l to a tuple and append it to tuple t as a single value '''
    return t[:] + (tuple(l),)  

def convert_lists(lol):
    t = []
    if type(lol) == a or type(lol) == tuple:
        return [convert_lists(lol) for i in t]
    return append_as_tuples(lol,a)

#- test harness#

a=[range(5), range(10,20), ['hello', 'goodbye']]  
print a  
print convert_lists(a)  
print convert_lists([])