def excel_key ( index ) : X = lambda n : ~ n and X ( ( n // 26 ) - 1 ) + chr ( 65 + ( n % 26 ) ) or '' return X ( int ( index ) )
python turning lambda expression into a key
create a key for index by converting index into a base - 26 number using A - Z as the characters .
def excel_key(index):
    """create a key for index by converting index into a base-26 number, using A-Z as the characters."""
    X = lambda n: ~n and X((n // 26)-1) + chr(65 + (n % 26)) or ''
    return X(int(index))