Python學習——set集合的補充

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set 是一個無序且不重複的元素集合
>>> num = {1,2,3,4,5} 

1.add()添加一個元素 
>>> num.add(6) 
>>> num 
>>> {1,2,3,4,5,6}

2.clear()清除集合中所有元素 
>>> num.clear() 
>>> num 
>>> set()

3.copy()複製一個集合 
>>> num1 = num.copy() 
>>> num1 
>>> {1,2,3,4,5}

4.difference()取得集合在一個或多個集合中不同的元素 
>>> num1 = {2,4,6,8,10} 
>>> num2 = {1,3,11,12,14} 
#返回在一個集合中不同的元素 
>>> num.difference(num1) 
>>> {1,3,5} 
#返回在多個集合中不同的元素 
>>> num.difference(num1,num2) 
>>> {5}

5.difference_update()刪除當前集合中所有包含在新集合裡的元素 
>>> num1 = {2,4,6,8,10} 
>>> num2 = {1,2,11,13} 
>>> num.difference_update(num1,num2) 
>>> num 
>>> {3,5}

6.discard()從集合中移除一個元素，如果元素不存在，不做任何處理 
>>> num.discard(1) 
>>> num 
>>> {2,3,4,5}

7.intersection()取交集，建立一個集合 
>>> num1 ={1,3,5,7,9} 
>>> num.intersection(num1) 
>>> {1,3,5}

8.intersection_update()取交集，修改與原來的集合 
>>> num1 = {1,3,5,7,9} 
>>> num.intersection_update(num1) 
>>> num 
>>> {1,3,5}

9.isdisjoint()如果沒有交集，返回True 
>>> num2 ={6,8,10} 
>>> num.isdisjoint(num2) 
>>> True

10.pop()從集合開頭移除一個元素 
>>> num.pop() 
>>> 1 
>>> num 
>>> {2,3,4,5} 
PS：如果集合為空白，返回錯誤提示

11.symmetric_difference()差集，建立新對象 
>>> num = {1,2,3,4,5,6} 
>>> num1 = {2,3,4,6,8,9} 
>>> num.symmetric_difference(num1) 
>>> {1,5,8,9}

12.symmetric_difference_update()差集，改變原來的集合 
>>> num = {1,2,3,4,5,6} 
>>> num1 = {2,3,4,6,8,9} 
>>> num.symmetric_difference_update(num1) 
>>> num 
>>> {1,5,8,9}

13.union()並集，返回一個新集合 
>>> num ={1,2,4,6,7} 
>>> num1 ={,2,4,6,8,10,12} 
>>> num.union(num1) 
>>> {1,2,4,6,7,8,10,12}

14.update()並集，並更新該集合 
>>> num ={1,2,4,6,7} 
>>> num1 ={,2,4,6,8,10,12} 
>>> num.update(num1) 
>>> num 
>>> {1,2,4,6,7,8,10,12}

小練習：

 1 old_dict = { 2     "#1": {‘hostname‘: ‘c1‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 80}, 3     "#2": {‘hostname‘: ‘c1‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 80}, 4     "#3": {‘hostname‘: ‘c1‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 80}      5 } 6 new_dict = { 7     "#1": {‘hostname‘: ‘c1‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 800}, 8     "#3": {‘hostname‘: ‘c1‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 80}, 9     "#4": {‘hostname‘: ‘c2‘, ‘cpu_count‘: 2, ‘mem_capicity‘: 80}     10 }11 old_set = set(old_dict.keys()) 12 update_list = list(old_set.intersection(new_dict.keys()))13 14 new_list = [] 15 del_list = []16 17 for i in new_dict.keys():     18 　　if i not in update_list:         19 　　　　new_list.append(i)20 for i in old_dict.keys():     21 　　if i not in update_list:         22 　　　　del_list.append(i)23 print (update_list,new_list,del_list,new_dict.keys()) 24 print(new_dict)

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結果為:
>>> [‘#1‘, ‘#3‘] [‘#4‘] [‘#2‘] dict_keys([‘#1‘, ‘#3‘, ‘#4‘])
>>>{
‘#1‘: {‘mem_capicity‘: 800, ‘hostname‘: ‘c1‘, ‘cpu_count‘: 2},
‘#3‘: {‘mem_capicity‘: 80, ‘hostname‘: ‘c1‘, ‘cpu_count‘: 2},
‘#4‘: {‘mem_capicity‘: 80, ‘hostname‘: ‘c2‘, ‘cpu_count‘: 2}
}

Python學習——set集合的補充