“集”这个概念在 Python 中算是比较年轻的,同时它的使用率也比较低。set 和它的不可变的姊妹类型 frozenset 直到 Python 2.3 才首次以 模块的形式出现,然后在 Python 2.6 中它们升级成为内置类型。本文记录相关内容。
l = ['spam', 'spam', 'eggs', 'spam']
s = set(l)
t = {1, 2}
-->
s
{'eggs', 'spam'}
t
{1, 2}
data = [1,2,3]
f = frozenset(data)
s = set([*data, f])
print(s)
-->
{frozenset({1, 2, 3}), 1, 2, 3}
set1 = set([1,2,3])
set2 = set([2,3,4])
set3 = set([4,5,6])
print(set1 | set2)
print(set1 - set2)
print(set2 & set2)
>>>
{1, 2, 3, 4}
{1}
{2, 3, 4}
<<<
s = {num for num in range(10) if num % 2}
print(s)
>>>
{1, 3, 5, 7, 9}
<<<