腾讯课堂——基础数据类型(set集合)

认识集合

　　由一个或多个确定的元素所构成的整体叫做集合。

　　集合中的元素有三个特征：

　　　　1.确定性（集合中的元素必须是确定的）

　　　　2.互异性（集合中的元素互不相同。例如：集合A={1，a}，则a不能等于1）

　　　　3.无序性（集合中的元素没有先后之分），如集合{3,4,5}和{3,5,4}算作同一个集合。　

　　*集合概念存在的目的是将不同的值存放到一起，不同的集合间用来做关系运算，无需纠结于集合中某个值

集合的定义

　　s = {1,2,3,1}

#定义可变集合
>>> set_test=set('hello')
>>> set_test
{'l', 'o', 'e', 'h'}
#改为不可变集合frozenset
>>> f_set_test=frozenset(set_test)
>>> f_set_test
frozenset({'l', 'e', 'h', 'o'})

集合的常用操作及关系运算

　　元素的增加

　　单个元素的增加 : add()，add的作用类似列表中的append

　　对序列的增加 : update()，而update类似extend方法，update方法可以支持同时传入多个参数：

>>> a={1,2}
>>> a.update([3,4],[1,2,7])
>>> a
{1, 2, 3, 4, 7}
>>> a.update("hello")
>>> a
{1, 2, 3, 4, 7, 'h', 'e', 'l', 'o'}
>>> a.add("hello")
>>> a
{1, 2, 3, 4, 'hello', 7, 'h', 'e', 'l', 'o'}　　

　　元素的删除

　　集合删除单个元素有两种方法：

　　　　元素不在原集合中时：

　　　　　　set.discard(x)不会抛出异常

　　　　　　set.remove(x)会抛出KeyError错误

>>> a={1,2,3,4}
>>> a.discard(1)
>>> a
{2, 3, 4}
>>> a.discard(1)
>>> a
{2, 3, 4}
>>> a.remove(1)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
KeyError: 1

　　pop()：由于集合是无序的，pop返回的结果不能确定，且当集合为空时调用pop会抛出KeyError错误，

　　clear():清空集合

>>> a={3,"a",2.1,1}
>>> a.pop()
1
>>> a.pop()
3
>>> a.clear()
>>> a
set()
>>> a.pop()
Traceback (most recent call last):
  File "<input>", line 1, in <module>
KeyError: 'pop from an empty set'　　

　　集合操作

         

　　　　|,|=:合集

a = {1,2,3}
b = {2,3,4,5}
print(a.union(b))
print(a|b)

　　　　&.&=:交集

a = {1,2,3}
b = {2,3,4,5}
print(a.intersection(b))
print(a&b)

　　　　－,－=:差集

a = {1,2,3}
b = {2,3,4,5}
print(a.difference(b))
print(a-b) 

　　　　^,^=:对称差集

a = {1,2,3}
b = {2,3,4,5}
print(a.symmetric_difference(b))
print(a^b)

 

　　包含关系

　　　　in,not in：判断某元素是否在集合内
　　　　＝＝,！＝:判断两个集合是否相等

　　　　两个集合之间一般有三种关系，相交、包含、不相交。在Python中分别用下面的方法判断：

• set.isdisjoint(s)：判断两个集合是不是不相交
• set.issuperset(s)：判断集合是不是包含其他集合，等同于a>=b
• set.issubset(s)：判断集合是不是被其他集合包含，等同于a<=b

　　　　
　　

集合的工厂函数

class set(object):
    """
    set() -> new empty set object
    set(iterable) -> new set object
Build an unordered collection of unique elements.
</span><span style="color: #800000;">"""</span>
<span style="color: #0000ff;">def</span> add(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    Add an element to a set.
    
    This has no effect if the element is already present.
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> clear(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Remove all elements from this set. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> copy(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return a shallow copy of a set. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> difference(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    相当于s1-s2
    
    Return the difference of two or more sets as a new set.
    
    (i.e. all elements that are in this set but not the others.)
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> difference_update(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Remove all elements of another set from this set. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> discard(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    与remove功能相同，删除元素不存在时不会抛出异常
    
    Remove an element from a set if it is a member.
    
    If the element is not a member, do nothing.
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> intersection(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    相当于s1&amp;s2
    
    Return the intersection of two sets as a new set.
    
    (i.e. all elements that are in both sets.)
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> intersection_update(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Update a set with the intersection of itself and another. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> isdisjoint(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return True if two sets have a null intersection. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> issubset(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> 
    相当于s1&lt;=s2
    
    Report whether another set contains this set. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> issuperset(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    相当于s1&gt;=s2
    
     Report whether this set contains another set. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> pop(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    Remove and return an arbitrary set element.
    Raises KeyError if the set is empty.
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> remove(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    Remove an element from a set; it must be a member.
    
    If the element is not a member, raise a KeyError.
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> symmetric_difference(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    相当于s1^s2
    
    Return the symmetric difference of two sets as a new set.
    
    (i.e. all elements that are in exactly one of the sets.)
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> symmetric_difference_update(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Update a set with the symmetric difference of itself and another. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> union(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    相当于s1|s2
    
    Return the union of sets as a new set.
    
    (i.e. all elements that are in either set.)
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> update(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Update a set with the union of itself and others. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__and__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&amp;value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__contains__</span>(self, y): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown; restored from __doc__</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> x.__contains__(y) &lt;==&gt; y in x. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__eq__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self==value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__getattribute__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return getattr(self, name). </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__ge__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&gt;=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__gt__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&gt;value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__iand__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&amp;=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__init__</span>(self, seq=()): <span style="color: #008000;">#</span><span style="color: #008000;"> known special case of set.__init__</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;">
    set() -&gt; new empty set object
    set(iterable) -&gt; new set object
    
    Build an unordered collection of unique elements.
    # (copied from class doc)
    </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__ior__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self|=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__isub__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self-=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__iter__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Implement iter(self). </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__ixor__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self^=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__len__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return len(self). </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__le__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&lt;=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__lt__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self&lt;value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span><span style="color: #000000;">

@staticmethod </span><span style="color: #008000;">#</span><span style="color: #008000;"> known case of __new__</span>
<span style="color: #0000ff;">def</span> <span style="color: #800080;">__new__</span>(*args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Create and return a new object.  See help(type) for accurate signature. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__ne__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self!=value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__or__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self|value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__rand__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return value&amp;self. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__reduce__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return state information for pickling. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__repr__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return repr(self). </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__ror__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return value|self. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__rsub__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return value-self. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__rxor__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return value^self. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__sizeof__</span>(self): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown; restored from __doc__</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> S.__sizeof__() -&gt; size of S in memory, in bytes </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__sub__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self-value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #0000ff;">def</span> <span style="color: #800080;">__xor__</span>(self, *args, **kwargs): <span style="color: #008000;">#</span><span style="color: #008000;"> real signature unknown</span>
    <span style="color: #800000;">"""</span><span style="color: #800000;"> Return self^value. </span><span style="color: #800000;">"""</span>
    <span style="color: #0000ff;">pass</span>

<span style="color: #800080;">__hash__</span> = None</pre>

 

课程回顾：

　　　　腾讯课堂第一课——流程控制 ：https://www.cnblogs.com/l-hf/p/11528934.html

　　　　腾讯课堂第二课——循     环 ：https://www.cnblogs.com/l-hf/p/11528937.html

　　　　腾讯课堂第三课——数字和字符串  ： https://www.cnblogs.com/l-hf/p/11528845.html

　　　　腾讯课堂第四课——列    表  ： https://www.cnblogs.com/l-hf/p/11528858.html

　　　　腾讯课堂第四课——字    典  ：https://www.cnblogs.com/l-hf/p/11528867.html

　　　　腾讯课堂第五课——元    祖  ：https://www.cnblogs.com/l-hf/p/11528864.htmll

更多相关内容，详见：

　　　  Python全栈开发入门经典：https://ke.qq.com/course/157698#tuin=839b573b 

　　　  Python全栈开发进阶实战：https://ke.qq.com/course/158006#tuin=839b573b