字典的‘魔法’方法

1 a = {'a':1,'b':2,'c':3,'d':4}
2 print(a.keys())
3 #结果：dict_keys(['a', 'b', 'c', 'd'])

1 a = {'a':1,'b':2,'c':3,'d':4}
2 print(a.values())
3 #结果：dict_values([1, 2, 3, 4])

1 a = {'a':1,'b':2,'c':3,'d':4}
2 print(a.items())
3 #结果：dict_items([('a', 1), ('b', 2), ('c', 3), ('d', 4)])

1 a = {'a':1,'b':2,'c':3,'d':4}
2 for i in a.keys():
3     print(i)
4 #结果：
5 '''a
6 b
7 c
8 d'''

1 a = {'a':1,'b':2,'c':3,'d':4}
2 for i in a.values():
3     print(i)
4 #结果：
5 '''1
6 2
7 3
8 4'''

1 a = {'a':1,'b':2,'c':3,'d':4}
2 for i in a.items():
3     print(i)
4 #结果：
5 '''('a', 1)
6 ('b', 2)
7 ('c', 3)
8 ('d', 4)'''

 1 a = {'a':1,'b':2,'c':3,'d':4}
 2 t = a.get('a',465456)
 3 print(t)
 4 #结果：1
 
 
 5 t1 = a.get('a')
 6 print(t1)
 7 #结果：1
 

 8 t2 = a.get('s',45645)
 9 print(t2)
 10 #结果：45645



 11 t3 = a.get('s')
 12 print(t3)
 13 #结果：None

 1 dic = {"k1": 'v1',"k2": 'v2'}
 2 v = dic.pop('k1','sb')
 3 print(dic,v)
 4 #结果：{'k2': 'v2'} v1
 

 5 v1 = dic.pop('k3','sb')
 6 print(dic,v1)
 7 #结果：{'k2': 'v2'} sb
 

 8 k3,v3 = dic.popitem()
 9 print(dic,k3,v3)
 10 #结果：{'k1': 'v1'} k2 v2

1 dic = {"k1": 'v1',"k2": 'v2'}
2 v = dic.setdefault('k1111','123')
3 print(dic,v)
4 #结果：{'k1': 'v1', 'k2': 'v2', 'k1111': '123'} 123




5 v1 = dic.setdefault('k1',1231)
6 print(v1)
7 #结果：v1

1 dic = {"k1": 'v1',"k2": 'v2'}
2 dic.update({'k1': '111111','k3': 123})
3 print(dic)
4 #结果：{'k1': '111111', 'k2': 'v2', 'k3': 123}
5 dic1 = {"k1": 'v1',"k2": 'v2'}
6 dic1.update(k1=123,k3=345,k5="asdf")
7 print(dic1)
8 #结果：{'k1': 123, 'k2': 'v2', 'k3': 345, 'k5': 'asdf'}

1 dic = {"k1": 'v1',"k2": 'v2'}
2 del dic['k1']
3 print(dic)
4 #结果：{'k2': 'v2'}