#a 与 b必须是两个相同类型的可迭代对象
a = "1"
b = "2"
print(set(a + b)) # {'1', '2'}
a = "123"
print(set(a + b)) # {'1', '2', '3'}
a = ['1', '3', 2]
b = ['2']
print(set(a + b)) # {'2', '3', 2, '1'}