Python3 集合的方法

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          <h3 id="python">《Python 教程》授课笔记附件</h3>
<ul>
<li>讲师: 魏明择</li>
<li>时间: 2019</li>
</ul>
<h5 id="python3">Python3 集合的方法</h5>
<table>
<thead>
<tr>
<th>方法</th>
<th>意义</th>
</tr>
</thead>
<tbody>
<tr>
<td>S.add(e)</td>
<td>在集合中添加一个新的元素e；如果元素已经存在，则不添加</td>
</tr>
<tr>
<td>S.remove(e)</td>
<td>从集合中删除一个元素，如果元素不存在于集合中，则会产生一个KeyError错误</td>
</tr>
<tr>
<td>S.discard(e)</td>
<td>从集合S中移除一个元素e,在元素e不存在时什么都不做;</td>
</tr>
<tr>
<td>S.clear()</td>
<td>清空集合内的所有元素</td>
</tr>
<tr>
<td>S.copy()</td>
<td>将集合进行一次浅拷贝</td>
</tr>
<tr>
<td>S.pop()</td>
<td>从集合S中删除一个随机元素;如果此集合为空，则引发KeyError异常</td>
</tr>
<tr>
<td>S.update(s2)</td>
<td>等同于 S l= s2, 用 S与s2得到的全集更新变量S</td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
<tr>
<td>S.difference(s2)</td>
<td>S - s2 补集运算，返回存在于在S中，但不在s2中的所有元素的集合</td>
</tr>
<tr>
<td>S.difference_update(s2)</td>
<td>等同于 S -= s2</td>
</tr>
<tr>
<td>S.intersection(s2)</td>
<td>等同于 S &amp; s2</td>
</tr>
<tr>
<td>S.intersection_update(s2)</td>
<td>等同于S &amp;= s2</td>
</tr>
<tr>
<td>S.isdisjoint(s2)</td>
<td>如果S与s2交集为空返回True,非空则返回False</td>
</tr>
<tr>
<td>S.issubset(s2)</td>
<td>如果S与s2交集为非空返回True,空则返回False</td>
</tr>
<tr>
<td>S.issuperset(...)</td>
<td>如果S为s2的超集返回True,否则返回False</td>
</tr>
<tr>
<td>S.symmetric_difference(s2)</td>
<td>返回对称补集, 等同于 S ^ s2</td>
</tr>
<tr>
<td>S.symmetric_difference_update(s2)</td>
<td>等同于 S ^= s2, 用 S 与 s2 的对称补集更新 S</td>
</tr>
<tr>
<td>S.union(s2)</td>
<td>生成 S 与 s2的全集, 等同于 S \</td>
</tr>
</tbody>
</table>
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