• Python set集合方法详解（全）

    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)
    False
    issubset() set1.issubset(set2) 判断 set1 是否是 set2 的子集 >>> set1 = {1,2,3}
    >>> set2 = {1,2}
    >>> set1.issubset(set2)
    False
    issuperset() set1.issuperset(set2) 判断 set2 是否是 set1 的子集 >>> set1 = {1,2,3}
    >>> set2 = {1,2}
    >>> set1.issuperset(set2)
    True
    pop() 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
    1
    remove() 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: 4
    symmetric_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}
6/48« 首页«45678»102030尾页 »

更多...

加载中...