python 集合（set)

1.集合的创建

集合是一个无序不重复元素的集。基本功能包括关系测试和消除重复元素。

创建集合：大括号或 set() 函数可以用来创建集合。注意：想要创建空集合，你必须使用 set() 而不是 {}，后者用于创建空字典。大括号也不可以创建元素含有字典与列表的集合。

 1 a={'a','b','c','d'}
 2 b=set('abcdefabcd')
 3 c=set({'a':1,'b':2})
 4 d=set(['a','b','c','a'])
 5 print(a,type(a))
 6 print(b,type(b))
 7 print(c,type(c))
 8 print(d,type(d))
 9 
10 #运行结果
11 {'c', 'd', 'b', 'a'} <class 'set'>
12 {'f', 'e', 'b', 'c', 'd', 'a'} <class 'set'>
13 {'b', 'a'} <class 'set'>
14 {'c', 'b', 'a'} <class 'set'>

demo

2.集合的功能属性

  1 class set(object):
  2     """
  3     set() -> new empty set object
  4     set(iterable) -> new set object
  5     
  6     Build an unordered collection of unique elements.
  7     """
  8     def add(self, *args, **kwargs): # real signature unknown
  9         """
 10         Add an element to a set.
 11         
 12         This has no effect if the element is already present.
 13         """
 14         pass
 15 
 16     def clear(self, *args, **kwargs): # real signature unknown
 17         """ Remove all elements from this set. """
 18         pass
 19 
 20     def copy(self, *args, **kwargs): # real signature unknown
 21         """ Return a shallow copy of a set. """
 22         pass
 23 
 24     def difference(self, *args, **kwargs): # real signature unknown
 25         """
 26         Return the difference of two or more sets as a new set.
 27         
 28         (i.e. all elements that are in this set but not the others.)
 29         """
 30         pass
 31 
 32     def difference_update(self, *args, **kwargs): # real signature unknown
 33         """ Remove all elements of another set from this set. """
 34         pass
 35 
 36     def discard(self, *args, **kwargs): # real signature unknown
 37         """
 38         Remove an element from a set if it is a member.
 39         
 40         If the element is not a member, do nothing.
 41         """
 42         pass
 43 
 44     def intersection(self, *args, **kwargs): # real signature unknown
 45         """
 46         Return the intersection of two sets as a new set.
 47         
 48         (i.e. all elements that are in both sets.)
 49         """
 50         pass
 51 
 52     def intersection_update(self, *args, **kwargs): # real signature unknown
 53         """ Update a set with the intersection of itself and another. """
 54         pass
 55 
 56     def isdisjoint(self, *args, **kwargs): # real signature unknown
 57         """ Return True if two sets have a null intersection. """
 58         pass
 59 
 60     def issubset(self, *args, **kwargs): # real signature unknown
 61         """ Report whether another set contains this set. """
 62         pass
 63 
 64     def issuperset(self, *args, **kwargs): # real signature unknown
 65         """ Report whether this set contains another set. """
 66         pass
 67 
 68     def pop(self, *args, **kwargs): # real signature unknown
 69         """
 70         Remove and return an arbitrary set element.
 71         Raises KeyError if the set is empty.
 72         """
 73         pass
 74 
 75     def remove(self, *args, **kwargs): # real signature unknown
 76         """
 77         Remove an element from a set; it must be a member.
 78         
 79         If the element is not a member, raise a KeyError.
 80         """
 81         pass
 82 
 83     def symmetric_difference(self, *args, **kwargs): # real signature unknown
 84         """
 85         Return the symmetric difference of two sets as a new set.
 86         
 87         (i.e. all elements that are in exactly one of the sets.)
 88         """
 89         pass
 90 
 91     def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
 92         """ Update a set with the symmetric difference of itself and another. """
 93         pass
 94 
 95     def union(self, *args, **kwargs): # real signature unknown
 96         """
 97         Return the union of sets as a new set.
 98         
 99         (i.e. all elements that are in either set.)
100         """
101         pass
102 
103     def update(self, *args, **kwargs): # real signature unknown
104         """ Update a set with the union of itself and others. """
105         pass
106 
107     def __and__(self, *args, **kwargs): # real signature unknown
108         """ Return self&value. """
109         pass
110 
111     def __contains__(self, y): # real signature unknown; restored from __doc__
112         """ x.__contains__(y) <==> y in x. """
113         pass
114 
115     def __eq__(self, *args, **kwargs): # real signature unknown
116         """ Return self==value. """
117         pass
118 
119     def __getattribute__(self, *args, **kwargs): # real signature unknown
120         """ Return getattr(self, name). """
121         pass
122 
123     def __ge__(self, *args, **kwargs): # real signature unknown
124         """ Return self>=value. """
125         pass
126 
127     def __gt__(self, *args, **kwargs): # real signature unknown
128         """ Return self>value. """
129         pass
130 
131     def __iand__(self, *args, **kwargs): # real signature unknown
132         """ Return self&=value. """
133         pass
134 
135     def __init__(self, seq=()): # known special case of set.__init__
136         """
137         set() -> new empty set object
138         set(iterable) -> new set object
139         
140         Build an unordered collection of unique elements.
141         # (copied from class doc)
142         """
143         pass
144 
145     def __ior__(self, *args, **kwargs): # real signature unknown
146         """ Return self|=value. """
147         pass
148 
149     def __isub__(self, *args, **kwargs): # real signature unknown
150         """ Return self-=value. """
151         pass
152 
153     def __iter__(self, *args, **kwargs): # real signature unknown
154         """ Implement iter(self). """
155         pass
156 
157     def __ixor__(self, *args, **kwargs): # real signature unknown
158         """ Return self^=value. """
159         pass
160 
161     def __len__(self, *args, **kwargs): # real signature unknown
162         """ Return len(self). """
163         pass
164 
165     def __le__(self, *args, **kwargs): # real signature unknown
166         """ Return self<=value. """
167         pass
168 
169     def __lt__(self, *args, **kwargs): # real signature unknown
170         """ Return self<value. """
171         pass
172 
173     @staticmethod # known case of __new__
174     def __new__(*args, **kwargs): # real signature unknown
175         """ Create and return a new object.  See help(type) for accurate signature. """
176         pass
177 
178     def __ne__(self, *args, **kwargs): # real signature unknown
179         """ Return self!=value. """
180         pass
181 
182     def __or__(self, *args, **kwargs): # real signature unknown
183         """ Return self|value. """
184         pass
185 
186     def __rand__(self, *args, **kwargs): # real signature unknown
187         """ Return value&self. """
188         pass
189 
190     def __reduce__(self, *args, **kwargs): # real signature unknown
191         """ Return state information for pickling. """
192         pass
193 
194     def __repr__(self, *args, **kwargs): # real signature unknown
195         """ Return repr(self). """
196         pass
197 
198     def __ror__(self, *args, **kwargs): # real signature unknown
199         """ Return value|self. """
200         pass
201 
202     def __rsub__(self, *args, **kwargs): # real signature unknown
203         """ Return value-self. """
204         pass
205 
206     def __rxor__(self, *args, **kwargs): # real signature unknown
207         """ Return value^self. """
208         pass
209 
210     def __sizeof__(self): # real signature unknown; restored from __doc__
211         """ S.__sizeof__() -> size of S in memory, in bytes """
212         pass
213 
214     def __sub__(self, *args, **kwargs): # real signature unknown
215         """ Return self-value. """
216         pass
217 
218     def __xor__(self, *args, **kwargs): # real signature unknown
219         """ Return self^value. """
220         pass
221 
222     __hash__ = None

set

3.集合的部分功能属性介绍

1)add(self, *args, **kwargs):

在集合里添加一个元素，不生成新的集合。

a={'a','b','c','d'}
b=a.add('e')
c=a.add('a')
print(a,type(a))
print(b,type(b))
print(c,type(c))

#运行结果
{'d', 'c', 'e', 'b', 'a'} <class 'set'>
None <class 'NoneType'>
None <class 'NoneType'>

demo

2）clear(self, *args, **kwargs):

清空集合里面的元素，不生成新的集合。

1 a={'a','b','c','d'}
2 b=a.clear()
3 print(a,type(a))
4 print(b,type(b))
5 
6 #运行结果
7 set() <class 'set'>
8 None <class 'NoneType'>

demo

3）copy(self, *args, **kwargs):

浅拷贝集合，返回一个新集合。

 1 a={1,(9,2),3}
 2 b=a.copy()
 3 print(a,id(a))
 4 print(b,id(b))
 5 
 6 #赋值
 7 c={1,2,3,4}
 8 d=c
 9 print(c,id(c))
10 print(d,id(d))
11 
12 #运行结果
13 {(9, 2), 1, 3} 13058696
14 {(9, 2), 1, 3} 13058576
15 {1, 2, 3, 4} 13059296
16 {1, 2, 3, 4} 13059296

demo

4）difference(self, *args, **kwargs):

与其他一个集合或多个集合对比，返回一个与其他集合不一样元素的集合。

1 a={'a','b','c','d'}
2 b=a.difference({'a',},{'b'})
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'c', 'b', 'a', 'd'}
8 {'c', 'd'} <class 'set'>

demo

5）difference_update(self, *args, **kwargs):

与其他一个集合或多个集合对比，删除集合与其他集合一样的元素，不返回新集合。

1 a={'a','b','c','d'}
2 b=a.difference_update({'a',},{'b'})
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'c', 'd'}
8 None <class 'NoneType'>

demo

6）discard(self, *args, **kwargs):

删除集合中的某个元素，如果这个元素没有在集合中，不做操作，不返回新集合。

1 a={'a','b','c','d'}
2 b=a.discard('a')
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'d', 'c', 'b'}
8 None <class 'NoneType'>

demo

7）intersection(self, *args, **kwargs):

返回一个和其他集合共同有的元素的集合。

1 a={'a','b','c','d'}
2 b=a.intersection({'a','e'},{'a','f'})
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'d', 'b', 'c', 'a'}
8 {'a'} <class 'set'>

demo

8)intersection_update(self, *args, **kwargs):

与其他一个集合或多个集合对比，删除集合中与其他集合不共有的元素，不返回新集合。

1 a={'a','b','c','d'}
2 b=a.intersection_update({'a','e'},{'a','f'})
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'a'}
8 None <class 'NoneType'>

demo

9）isdisjoint(self, *args, **kwargs):

对比两个集合，有空交集则返回True，没有则返回False。

 1 a={'a','b','c','d','    '}       #空元素用tab键输入
 2 b=a.isdisjoint({'a','e'})
 3 c=a.isdisjoint({'   ','f'})
 4 print(a)
 5 print(b,type(b))
 6 print(c,type(c))
 7 
 8 #运行结果
 9 {'a', 'b', '    ', 'c', 'd'}
10 False <class 'bool'>
11 True <class 'bool'>

demo

10）issubset(self, *args, **kwargs):

判断集合的包含关系，其他集合如果包含原集合则返回True,不包含则返回Fasle。

 1 a={'a','b','c','d',}
 2 b={'a','b','c','d','f'}
 3 c=a.issubset(b)
 4 d=a.issubset({'a'})
 5 print(a)
 6 print(b)
 7 print(c,type(c))
 8 print(d,type(d))
 9 
10 #运行结果
11 {'d', 'a', 'b', 'c'}
12 {'f', 'b', 'a', 'd', 'c'}
13 True <class 'bool'>
14 False <class 'bool'>

demo

11）issuperset(self, *args, **kwargs):

判断集合的包含关系，原集合如果包含其他集合则返回True,不包含则返回Fasle。

 1 a={'a','b','c','d',}
 2 b={'a','b','c','d','f'}
 3 c=a.issuperset(b)
 4 d=a.issuperset({'a'})
 5 print(a)
 6 print(b)
 7 print(c,type(c))
 8 print(d,type(d))
 9 
10 #运行结果
11 {'a', 'b', 'c', 'd'}
12 {'a', 'b', 'd', 'c', 'f'}
13 False <class 'bool'>
14 True <class 'bool'>

demo

12）pop(self, *args, **kwargs):

从集合中取出一个元素，如果集合为空，则报TypeError错误。

1 a={'a','b','c','d',}
2 b=a.pop()
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'c', 'b', 'a'}
8 d <class 'str'>   #因为集合是无序的，所以取出的值是随机的

demo

13）remove(self, *args, **kwargs):

移除集合中的一个元素，这个元素必须在集合中，如果不在，则报TypeError错误。

1 a={'a','b','c','d',}
2 b=a.remove('b')
3 print(a)
4 print(b,type(b))
5 
6 #运行结果
7 {'c', 'a', 'd'}
8 None <class 'NoneType'>

demo

14）union(self, *args, **kwargs):

两个集合拼接返回一个新集合。

 1 a={'a','b','c','d',}
 2 b=a.union('b')
 3 c=a.union({'e','f'})
 4 print(a)
 5 print(b,type(b))
 6 print(c,type(c))
 7 
 8 #运行结果
 9 {'b', 'd', 'c', 'a'}
10 {'b', 'd', 'c', 'a'} <class 'set'>
11 {'d', 'c', 'e', 'b', 'f', 'a'} <class 'set'>

demo

15）update(self, *args, **kwargs):

更新集合，添加集合中没有的新元素，不返回新集合。

 1 a={'a','b','c','d',}
 2 b=a.update('b')
 3 c=a.update({'e','f'})
 4 print(a)
 5 print(b,type(b))
 6 print(c,type(c))
 7 
 8 #运行结果
 9 {'a', 'c', 'b', 'e', 'd', 'f'}
10 None <class 'NoneType'>
11 None <class 'NoneType'>

demo

16）__and__(self, *args, **kwargs):

和intersection()一样，返回一个和其他集合共同有的元素的集合，但是前者可以和多个集合一起对比，后者只可以和一个集合对比。

 1 a={'a','b','c','d',}
 2 b=a.__and__('b')
 3 c=a.__and__({'a','f'})
 4 print(a)
 5 print(b,type(b))
 6 print(c,type(c))
 7 
 8 #运行结果
 9 {'a', 'b', 'd', 'c'}
10 NotImplemented <class 'NotImplementedType'>
11 {'a'} <class 'set'>

demo

17）__contains__(self, y):

判断集合中有没有包含某个元素或集合，包含则返回True，不包含则返回Fasle。

 1 a={'a','b','c','d',}
 2 b=a.__contains__('b')
 3 c=a.__contains__({'a','f'})
 4 print(a)
 5 print(b,type(b))
 6 print(c,type(c))
 7 
 8 #运行结果
 9 {'a', 'd', 'c', 'b'}
10 True <class 'bool'>
11 False <class 'bool'>

demo