python学习（Day03）

Posted 2020-07-10

set

set集合，是一个无序且不重复的元素集合，集合对象还支持union(联合), intersection(交), difference(差)和sysmmetric difference(对称差集)等数学运算.  

不重复性

1 >>> a = [1,1,2,2,3,3,4,4,]
2 >>> set(a)
3 {1, 2, 3, 4}

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无序性

1 #!/usr/bin/python
2 # -*- coding: UTF-8 -*-
3 a = [‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘,]
4 b = set(a)
5 print(b)
6 
7 #输出结果
8 {‘zhi‘, ‘yu‘, ‘gong‘, ‘shang‘, ‘jue‘}

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set（object）

1.def difference(self,*args,**kwargs): # difference()用来查找a中存在，而b中不存在的元素

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘gong‘,‘jue‘,‘yu‘,‘wen‘,‘wu‘])
3 c = a.difference(b)
4 print(c)
5 
6 # 输出结果
7 {‘zhi‘, ‘shang‘}

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2.def intersection(self,*args,**kwargs): # instersection()用来查找a,b中共同存在的元素（交集）

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘gong‘,‘jue‘,‘yu‘,‘wen‘,‘wu‘])
3 c = a.intersection(b)
4 print(c)
5 
6 # 输出结果
7 {‘gong‘, ‘jue‘, ‘yu‘}

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3.def symmetric_difference(self,*args,**kwargs): # symmetric_difference()用来查找对称差集，即a，b中不想交的元素，与instersection()相反

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘gong‘,‘jue‘,‘yu‘,‘wen‘,‘wu‘])
3 c = a.symmetric_difference(b)
4 print(c)
5 
6 #输出结果
7 {‘shang‘, ‘wen‘, ‘zhi‘, ‘wu‘}

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4.def discard(self,*args,**kwargs):及 def remove(self,*args,**kwargs): # discard()用来删除指定元素，元素不存在不报错，remove()也是用来删除指定元素，但是元素不存在会报错

 1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
 2 a.discard(‘gong‘)
 3 print(a)
 4 
 5 #输出结果
 6 {‘jue‘, ‘yu‘, ‘shang‘, ‘zhi‘}
 7 
 8 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
 9 a.discard(‘wu‘)
10 print(a)
11 
12 #输出结果
13 #为空，没有报错
14 
15 
16 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
17 a.remove(‘shang‘)
18 print(a)
19 
20 #输出结果
21 {‘gong‘, ‘zhi‘, ‘jue‘, ‘yu‘}
22 
23 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
24 a.remove(‘wu‘)
25 print(a)
26 
27 #输出结果
28 #报错
29 Traceback (most recent call last):
30   File "C:/Users/Administrator/PycharmProjects/untitled4/mxzheng/a/a1.py", line 9, in <module>
31     a.remove(‘wu‘)
32 KeyError: ‘wu‘

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5.def update(self,*args,**kwargs): # update()用来更新

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘ma‘,‘xiao‘,‘zheng‘])
3 a.update(b)
4 print(a)
5 
6 #输出结果
7 {‘gong‘, ‘zhi‘, ‘ma‘, ‘jue‘, ‘yu‘, ‘shang‘, ‘zheng‘, ‘xiao‘}

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6.def union(self,*args,**kwargs): # union()用来查找a,b中所有元素（并集）

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘wen‘,‘wu‘,‘shen‘,‘shang‘])
3 c = a.union(b)
4 print(c)
5 
6 #输出结果
7 {‘shen‘, ‘wu‘, ‘yu‘, ‘zhi‘, ‘wen‘, ‘jue‘, ‘gong‘, ‘shang‘}

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7.def intersection_update(self,*args,**kwargs): # intersection_update() 查找a,b的交集并更新到a

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘shen‘,‘shang‘])
3 a.intersection_update(b)
4 print(a)
5 
6 #输出结果
7 {‘shang‘}

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8.def symmetric_difference_update(self,*args,**kwargs): # symmetric_difference_update() 查找a，b的对称差集，并更新到a

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘shen‘,‘shang‘])
3 a.symmetric_difference_update(b)
4 print(a)
5 
6 #输出结果
7 {‘zhi‘, ‘gong‘, ‘yu‘, ‘shen‘, ‘jue‘}

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9.def issubset(self,*args,**kwargs):和 def issuperset(self,*args,**kwargs): # issubset用来查看b是否为a的子序列，issuperset()用来查看a是否为b的父序列，返回结果True or False

 1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
 2 b = set([‘gong‘,‘shang‘])
 3 c = a.issubset(b)
 4 print(c)
 5 
 6 #输出结果
 7 False
 8 ...
 9 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
10 b = set([‘gong‘,‘shang‘])
11 c = b.issubset(a)
12 print(c)
13 
14 #输出结果
15 True
16 
17 ...
18 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
19 b = set([‘gong‘,‘shang‘])
20 c = a.issuperset(b)
21 print(c)
22 
23 #输出结果
24 Ture
25 
26 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
27 b = set([‘gong‘,‘shang‘])
28 c = b.issuperset(a)
29 print(c)
30 
31 #输出结果
32 False

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 10.def add(self,*args,**kwargs): #add() #用来添加元素

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = (1,2,3,4,5)
3 a.add(b)
4 print(a)
5 
6 #输出结果
7 {‘zhi‘, (1, 2, 3, 4, 5), ‘gong‘, ‘jue‘, ‘shang‘, ‘yu‘}

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11.def clear(self,*args,**kwargs): #用来清除集合中所有的元素

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 a.clear()
3 print(a)
4 
5 #输出结果
6 set()

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12.def difference_update(self,*args,**kwargs): # 从a集合中从删除和b的交集

1 a = set([‘gong‘,‘shang‘,‘jue‘,‘zhi‘,‘yu‘])
2 b = set([‘gong‘,‘shang‘])
3 a.difference_update(b)
4 print(a)
5 
6 #输出结果
7 {‘yu‘, ‘zhi‘, ‘jue‘}

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