(base, lst, rank=1, mode='_')
return str_lst
Construct a list of strings of the form 'base+mode+indexes' where the
    indexes are formed by converting 'lst' to a list of strings and then
    forming the 'indexes' by concatenating combinations of elements from
    'lst' taken 'rank' at a time.
Construct a list of strings of the form 'base+mode+indexes' where the
    indexes are formed by converting 'lst' to a list of strings and then
    forming the 'indexes' by concatenating combinations of elements from
    'lst' taken 'rank' at a time.
Construct a list of strings of the form base + mode + indexes where the indexes are formed by converting lst to a list of strings and then forming the indexes by concatenating combinations of elements from lst taken rank at a time .
def str_combinations(base, lst, rank=1, mode='_'):
    """
    Construct a list of strings of the form 'base+mode+indexes' where the
    indexes are formed by converting 'lst' to a list of strings and then
    forming the 'indexes' by concatenating combinations of elements from
    'lst' taken 'rank' at a time.
    """
    str_lst = list(map(lambda x: base + mode + x, map(lambda x: reduce(operator.add, x),
                        combinations(map(lambda x: str(x), lst), rank))))
    return str_lst
def str_combinations ( base , lst , rank = 1 , mode = '_' ) : str_lst = list ( map ( lambda x : base + mode + x , map ( lambda x : reduce ( operator . add , x ) , combinations ( map ( lambda x : str ( x ) , lst ) , rank ) ) ) ) return str_lst