Python set集合方法详解（全）

参考链接： Python set集合 difference_update ()

前面学习了 set 集合，本节来一一学习 set 类型提供的方法。首先，通过 dir(set) 命令可以查看它有哪些方法： 

>>> dir(set)

['add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update'] 

各个方法的具体语法结构及功能如表 1 所示。   

  表 1 Python set方法

 方法名语法格式功能实例add()set1.add()向 set1 集合中添加数字、字符串、元组或者布尔类型>>> set1 = {1,2,3} >>> set1.add((1,2)) >>> set1 {(1, 2), 1, 2, 3}clear()set1.clear()清空 set1 集合中所有元素>>> set1 = {1,2,3} >>> set1.clear() >>> set1 set() set()才表示空集合，{}表示的是空字典copy()set2 = set1.copy()拷贝 set1 集合给 set2>>> set1 = {1,2,3} >>> set2 = set1.copy() >>> set1.add(4) >>> set1 {1, 2, 3, 4} >>> set1 {1, 2, 3}difference() set3 = set1.difference(set2)将 set1 中有而 set2 没有的元素给 set3>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set3 = set1.difference(set2) >>> set3 {1, 2}difference_update()set1.difference_update(set2)从 set1 中删除与 set2 相同的元素>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set1.difference_update(set2) >>> set1 {1, 2}discard()set1.discard(elem)删除 set1 中的 elem 元素>>> set1 = {1,2,3} >>> set1.discard(2) >>> set1 {1, 3} >>> set1.discard(4) {1, 3}intersection()set3 = set1.intersection(set2)取 set1 和 set2 的交集给 set3>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set3 = set1.intersection(set2) >>> set3 {3}intersection_update()set1.intersection_update(set2)取 set1和 set2 的交集，并更新给 set1>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set1.intersection_update(set2) >>> set1 {3}isdisjoint()set1.isdisjoint(set2)判断 set1 和 set2 是否没有交集，有交集返回 False；没有交集返回 True>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set1.isdisjoint(set2) Falseissubset()set1.issubset(set2)判断 set1 是否是 set2 的子集>>> set1 = {1,2,3} >>> set2 = {1,2} >>> set1.issubset(set2) Falseissuperset()set1.issuperset(set2)判断 set2 是否是 set1 的子集>>> set1 = {1,2,3} >>> set2 = {1,2} >>> set1.issuperset(set2) Truepop()a = set1.pop()取 set1 中一个元素，并赋值给 a>>> set1 = {1,2,3} >>> a = set1.pop() >>> set1 {2,3} >>> a 1remove()set1.remove(elem)移除 set1 中的 elem 元素>>> set1 = {1,2,3} >>> set1.remove(2) >>> set1 {1, 3} >>> set1.remove(4) Traceback (most recent call last):   File "<pyshell#90>", line 1, in <module>     set1.remove(4) KeyError: 4symmetric_difference()set3 = set1.symmetric_difference(set2)取 set1 和 set2 中互不相同的元素，给 set3>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set3 = set1.symmetric_difference(set2) >>> set3 {1, 2, 4}symmetric_difference_update()set1.symmetric_difference_update(set2)取 set1 和 set2 中互不相同的元素，并更新给 set1>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set1.symmetric_difference_update(set2) >>> set1 {1, 2, 4}union()set3 = set1.union(set2)取 set1 和 set2 的并集，赋给 set3>>> set1 = {1,2,3} >>> set2 = {3,4} >>> set3=set1.union(set2) >>> set3 {1, 2, 3, 4}update()set1.update(elem)添加列表或集合中的元素到 set1>>> set1 = {1,2,3} >>> set1.update([3,4]) >>> set1 {1,2,3,4}