Переменные класса и Python3

class TestMe:
    CONSTANT = (('1', 'One'), ('2', 'Two'), ('3', 'Three'))
    FILTER = (0, 1)
 
    test1 = ','.join([x[1] for x in CONSTANT])
    # Работает и в 2ке и в 3ке, содержит 'One,Two,Three'
 
    test2 = ','.join([CONSTANT[x][1] for x in FILTER])
    # Во 2м питоне ошибок нет, содержит 'One,Two'
    # В python 3 выдаёт ошибку: NameError: name 'CONSTANT' is not defined
 
 
t = TestMe()
 
print(t.test1)
print(t.test2)

class TestMe(object):
    CONSTANT = (('1', 'One'), ('2', 'Two'), ('3', 'Three'))
    FILTER = (0, 1)
 
    def test1(self):
        return ','.join(x[1] for x in self.CONSTANT)
 
    def test2(self):
        return ','.join(self.CONSTANT[x][1] for x in self.FILTER)
 
 
t = TestMe()
 
print(t.test1())
print(t.test2())

def filter_me_for_the_class_var(arg, filtr):
    return ','.join([arg[x][1] for x in filtr])
 
...
        test2 = filter_me_for_the_class_var(CONSTANT, FILTER)

test2 = ','.join([x[1] for x in map(CONSTANT.__getitem__, FILTER)])

from operator import itemgetter
...
test2 = ','.join([x[1] for x in itemgetter(*FILTER)(CONSTANT)])

test2 = (lambda CONSTANT, FILTER : ','.join([CONSTANT[x][1] for x in FILTER]))(CONSTANT, FILTER)