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.

"""

def add(self, *args, **kwargs): # real signature unknown

"""

Add an element to a set.
This has no effect if the element is already present.

"""

pass
def clear(self, *args, **kwargs): # real signature unknown

""" Remove all elements from this set. """

pass
def copy(self, *args, **kwargs): # real signature unknown

""" Return a shallow copy of a set. """

pass
def difference(self, *args, **kwargs): # real signature unknown

"""

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.)

"""

pass
def difference_update(self, *args, **kwargs): # real signature unknown

""" Remove all elements of another set from this set. """

pass
def discard(self, *args, **kwargs): # real signature unknown

"""

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.

"""

pass
def intersection(self, *args, **kwargs): # real signature unknown

"""

相当于s1&s2
Return the intersection of two sets as a new set.
(i.e. all elements that are in both sets.)

"""

pass
def intersection_update(self, *args, **kwargs): # real signature unknown

""" Update a set with the intersection of itself and another. """

pass
def isdisjoint(self, *args, **kwargs): # real signature unknown

""" Return True if two sets have a null intersection. """

pass
def issubset(self, *args, **kwargs): # real signature unknown

"""

相当于s1<=s2
Report whether another set contains this set. """

pass
def issuperset(self, *args, **kwargs): # real signature unknown

"""

相当于s1>=s2
Report whether this set contains another set. """

pass
def pop(self, *args, **kwargs): # real signature unknown

"""

Remove and return an arbitrary set element.

Raises KeyError if the set is empty.

"""

pass
def remove(self, *args, **kwargs): # real signature unknown

"""

Remove an element from a set; it must be a member.
If the element is not a member, raise a KeyError.

"""

pass
def symmetric_difference(self, *args, **kwargs): # real signature unknown

"""

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.)

"""

pass
def symmetric_difference_update(self, *args, **kwargs): # real signature unknown

""" Update a set with the symmetric difference of itself and another. """

pass
def union(self, *args, **kwargs): # real signature unknown

"""

相当于s1|s2
Return the union of sets as a new set.
(i.e. all elements that are in either set.)

"""

pass
def update(self, *args, **kwargs): # real signature unknown

""" Update a set with the union of itself and others. """

pass
def and(self, *args, **kwargs): # real signature unknown

""" Return self&value. """

pass
def contains(self, y): # real signature unknown; restored from doc

""" x.contains(y) <==> y in x. """

pass
def eq(self, *args, **kwargs): # real signature unknown

""" Return self==value. """

pass
def getattribute(self, *args, **kwargs): # real signature unknown

""" Return getattr(self, name). """

pass
def ge(self, *args, **kwargs): # real signature unknown

""" Return self>=value. """

pass
def gt(self, *args, **kwargs): # real signature unknown

""" Return self>value. """

pass
def iand(self, *args, **kwargs): # real signature unknown

""" Return self&=value. """

pass
def init(self, seq=()): # known special case of set.init

"""

set() -> new empty set object

set(iterable) -> new set object
Build an unordered collection of unique elements.

# (copied from class doc)

"""

pass
def ior(self, *args, **kwargs): # real signature unknown

""" Return self|=value. """

pass
def isub(self, *args, **kwargs): # real signature unknown

""" Return self-=value. """

pass
def iter(self, *args, **kwargs): # real signature unknown

""" Implement iter(self). """

pass
def ixor(self, *args, **kwargs): # real signature unknown

""" Return self^=value. """

pass
def len(self, *args, **kwargs): # real signature unknown

""" Return len(self). """

pass
def le(self, *args, **kwargs): # real signature unknown

""" Return self<=value. """

pass
def lt(self, *args, **kwargs): # real signature unknown

""" Return self<value. """

pass
@staticmethod # known case of new

def new(*args, **kwargs): # real signature unknown

""" Create and return a new object.  See help(type) for accurate signature. """

pass
def ne(self, *args, **kwargs): # real signature unknown

""" Return self!=value. """

pass
def or(self, *args, **kwargs): # real signature unknown

""" Return self|value. """

pass
def rand(self, *args, **kwargs): # real signature unknown

""" Return value&self. """

pass
def reduce(self, *args, **kwargs): # real signature unknown

""" Return state information for pickling. """

pass
def repr(self, *args, **kwargs): # real signature unknown

""" Return repr(self). """

pass
def ror(self, *args, **kwargs): # real signature unknown

""" Return value|self. """

pass
def rsub(self, *args, **kwargs): # real signature unknown

""" Return value-self. """

pass
def rxor(self, *args, **kwargs): # real signature unknown

""" Return value^self. """

pass
def sizeof(self): # real signature unknown; restored from doc

""" S.sizeof() -> size of S in memory, in bytes """

pass
def sub(self, *args, **kwargs): # real signature unknown

""" Return self-value. """

pass
def xor(self, *args, **kwargs): # real signature unknown

""" Return self^value. """

pass
hash = None

 

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