def string_to_char(l):
    '''Convert 1-D list of strings to 2-D list of chars.'''

    if not l:
        return []

    if l == ['']:
        l = [' ']

    maxlen = reduce(max, map(len, l))
    ll = [x.ljust(maxlen) for x in l]
    result = []
    for s in ll:
        result.append([x for x in s])
    return result
Convert 1-D list of strings to 2-D list of chars.