def test_01():
    stack = []
    return not stack

def test_02():
    stack = [1,2,3]
    return not stack

def test_03():
    stack = [1,2,3]
    return stack


s = test_01()
print(s)

s = test_02()
print(s)

s = test_03()
print(s)

print(not 0)
print(not [])
print(not 2)
print(not [2,3,4])


