set

去重

In [20]: set(['a', 'd', 'c', 's', 'a'])
Out[20]: {'a', 'c', 'd', 's'}
In [25]: lst = [1, 2, 3, 1]
In [26]: set(i for i in lst)
Out[26]: {1, 2, 3}

交集

In [28]: set(a) & set(b)
Out[28]: {1}

差集

In [29]: set(a) ^ set(b)
Out[29]: {2, 3, 4, 5}

并集

In [30]: set(a) | set(b)
Out[30]: {1, 2, 3, 4, 5}