【5.2】dict的常用方法

 1 #!/user/bin/env python
 2 # -*- coding:utf-8 -*-
 3 import copy
 4 a = {'zy': 123}
 5 
 6 # clear
 7 a.clear()
 8 print(a)
 9 
10 # copy,返回浅拷贝
11 b = {'zy': {'school': 'hx'}}
12 new_dict = b.copy()
13 new_dict['zy']['school'] = 'hx1'
14 print(b)
15 
16 # 深拷贝
17 c = {'zy': {'school': 'hx'}}
18 new_dict = copy.deepcopy(c)
19 new_dict['zy']['school'] = 'hx1'
20 print(c)
21 
22 # fromkeys
23 new_list = ['zy1', 'zy2']
24 # fromkeys,第一个参数是一个可迭代对象，第二个参数是value的默认值
25 new_dict = dict.fromkeys(new_list, {'school': 'hx'})
26 print(new_dict)
27 
28 # get
29 value = new_dict.get('zy', None)
30 print(value)
31 
32 # item
33 for key, value in new_dict.items():
34     print(key, value)
35 
36 # setdefault, 在get的基础之上，如果在dict中没有get到值，那么不仅仅返回设置的默认值，还会将这个key，value加入到dict中
37 value = new_dict.setdefault('zy', None)
38 print(value)
39 print(new_dict)
40 
41 # update,将key，value插入到dict中
42 new_dict.update({'zy111': 111})
43 new_dict.update(zy222=222, zy333=333)
44 new_dict.update([('zy444','444')])
45 new_dict.update((('zy555','555'),))
46 print(new_dict)

{}
{'zy': {'school': 'hx1'}}
{'zy': {'school': 'hx'}}
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}}
None
zy1 {'school': 'hx'}
zy2 {'school': 'hx'}
None
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}, 'zy': None}
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}, 'zy': None, 'zy111': 111, 'zy222': 222, 'zy333': 333, 'zy444': '444', 'zy555': '555'}