Python学习【第八篇】Set集合

Set集合

set集合是无序,不能重复,可嵌套的序列

如何创建

li = []
dic = {"k1":123}
se = {"123","456"}

# 查看它的类型
print (type(se))

# 输出
<class 'set'>

--------------------------------------------------------------
# 创建： 

s1 = {11,22}

s2 = set()  # 创建一个空集合

s3 = set([11,22,33,44])

---------------------------------------------------------------
# set集合无序，且不重复的序列

li = [11,22,11,33]
s4 = set(li)
print(s4)

# 输出
{33, 11, 22}

功能

·添加元素

s = set()
s.add(123)
print(s)

# 输出
{123}

# PS:添加相同元素，不会生效，因为之前说过set是不重复的序列
s.add(123)
s.add(123)
print(s)

# 输出
{123}

·清楚所有内容

s.clear()
print(s)

# 输出
set()

·浅拷贝

s.add(456)
s1 = s.copy()
print(s1)

# 输出
{456}

·取不同

s1 = {11,22,33}
s2 = {22,33,44}

----------------------------------------------------------

# s1中存在，s2中不存在
s3 = s1.difference(s2)
print(s3)

# 输出
{11}

----------------------------------------------------------

# s1中存在，s2中不存在，并更新到s1
s1.difference_update(s2)
print(s1)

# 输出
{11}

-----------------------------------------------------------

# 取s1，s2中不同的元素
s4 = s1.symmetric_difference(s2)
print(s4)

# 输出
{11,44}

------------------------------------------------------------

# 取s1，s2中不同的元素,并更新到s1
s1.symmetric_difference_update(s2)
print(s1)

# 输出
{11,44}

·移除

#移除指定元素（不存在不报错）
s1 = {11,22,33}
s1.discard(11)
print(s1)

# 输出
{33, 22}

---------------------------------------------------

# 移除指定元素（但报错）
s1.remove(1111)
print(s1)

---------------------------------------------------

# 随机移除
s2 = {11,22,33}
ret = s2.pop()
print(ret)
print(s2)

# 输出
33
{11,22}

·交集

s1 = {11,22,33}
s2 = {22,33,44}
s3 = s1.intersetion(s2)
print(s3)

# 输出
{33, 22}

-------------------------------------------

# 计算出交集直接更新到s1
s1.intersection_update(s2)
print(s1)

# 输出
{33,22}

·并集

s1 = {11,22,33}
s2 = {22,33,44}
s3 = s1.union(s2)
print(s3)

# 输出
{33, 22, 11, 44}

·更新

# 批量更新可以迭代的对象
s1 = {11,22,33}
li = [44,22,33,11,55]

# 更新列表
s1.update(li)
print(s1)

# 输出
{33, 11, 44, 22, 55}

-------------------------------------------------

# 更新字符串
s1 = {11,22,33}
a = "boubon"
s1.update(a)
print(s1)

# 输出
{33, 'n', 11, 'o', 'u', 22, 'b'}

 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，添加元素

         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. 清除内容"""
         pass

     def copy(self, *args, **kwargs): # real signature unknown
         """ Return a shallow copy of a set. 浅拷贝  """
         pass

     def difference(self, *args, **kwargs): # real signature unknown
         """
         Return the difference of two or more sets as a new set. A中存在，B中不存在

         (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.  从当前集合中删除和B中相同的元素"""
         pass

     def discard(self, *args, **kwargs): # real signature unknown
         """
         Remove an element from a set if it is a member.

         If the element is not a member, do nothing. 移除指定元素，不存在不保错
         """
         pass

     def intersection(self, *args, **kwargs): # real signature unknown
         """
         Return the intersection of two sets as a new set. 交集

         (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.  取交集并更更新到A中 """
         pass

     def isdisjoint(self, *args, **kwargs): # real signature unknown
         """ Return True if two sets have a null intersection.  如果没有交集，返回True，否则返回False"""
         pass

     def issubset(self, *args, **kwargs): # real signature unknown
         """ Report whether another set contains this set.  是否是子序列"""
         pass

     def issuperset(self, *args, **kwargs): # real signature unknown
         """ Report whether this set contains another set. 是否是父序列"""
         pass

     def pop(self, *args, **kwargs): # real signature unknown
         """
         Remove and return an arbitrary set element.
         Raises KeyError if the set is empty. 移除元素
         """
         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. 移除指定元素，不存在保错
         """
         pass

     def symmetric_difference(self, *args, **kwargs): # real signature unknown
         """
         Return the symmetric difference of two sets as a new set.  对称差集

         (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. 对称差集，并更新到a中 """
         pass

     def union(self, *args, **kwargs): # real signature unknown
         """
         Return the union of sets as a new set.  并集

         (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. 更新 """
         pass

set(object)

类CMDB的小实验

old_dic = {
    "#1": 8,
    "#2": 4,
    "#4": 2,
}

new_dic = {
    "#1": 4,
    "#2": 4,
    "#3": 2,
}

'''
应该删除哪几个槽位
    需求分析:
    1.old_dic存在,new_dic不存在的key
        old_keys = old_dic.keys()
        old_set = set(old_keys)

        new_keys = new_dic.keys()
        new_set = set(new_keys)

        old_set.differents(new_set)
应该更新哪几个槽位
应该增加哪几个槽位
'''

old_keys = set(old_dic.keys())
new_keys = set(new_dic.keys())

remove_set = old_keys.difference(new_keys)
add_set = new_keys.difference(old_keys)
update_set = old_keys.intersection(new_keys)