3-3 字典

1、字典的定义

1 stu_info = {"name":"王志华","age":18,"addr":"北京"}
2 # key - value

2、查询

1 #查
2 print(stu_info)
3 print(stu_info['name'])
4 print(stu_info['age'])
5 print(stu_info['money'])  #取key不存在的 KeyError: 'money'

3、修改元素

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #修改
3 stu_info['addr'] ='上海'
4 print(stu_info)

4、新增字典元素

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #新增
3 stu_info['phone'] = 1234567
4 stu_info.setdefault('email','sfsfs@163.com')
5 #你用setdefault新增一个已经存在的key,它不会改变原来key的value
6 stu_info.setdefault('age',29)
7 print(stu_info)
8 #{'name': '王志华', 'age': 18, 'addr': '北京', 'phone': 1234567, 'email': 'sfsfs@163.com'}

5、删除字典元素

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #删除
3 stu_info.pop('addr')
4 del stu_info['age']  #
5 stu_info.clear() #清空这个字典
6 stu_info.popitem()#从字典里面随机删除一个元素
7 print(stu_info)

6、合并两个字典

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #删除
3 stu_info.pop('addr')
4 del stu_info['age']  #
5 stu_info.clear() #清空这个字典
6 stu_info.popitem()#从字典里面随机删除一个元素
7 print(stu_info)
8 #{'b': 1, 'a': 'v'}

7、获取字典中所有的key值和value值

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 print(stu_info.keys())   #获取字典里面所有的key
3 # dict_keys(['name', 'age', 'addr'])
4 print(stu_info.values()) #获取字典里面所有的value
5 # dict_values(['王志华', 18, '北京'])

8、循环字典，每次循环的是字典的key

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #直接循环字典，看看每次循环的是字典的key
3 for i in stu_info:
4     print(i,stu_info[i])

　　循环字典，每次循环的是字典的key，也可以打印出对应的value值

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 #直接循环字典，看看每次循环的是字典的key
3 for i in stu_info:
4     # print(i,stu_info[i])
5     s = " %s => %s" % (i, stu_info.get(i))
6     print(s)

7 # name => 王志华
8 #  age => 18
9 #  addr => 北京

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 print(stu_info.items())
3 
4 for k,v in stu_info.items():
5     print(" %s => %s" %(k,v))

9、判断key是否存在

1 stu_info = {"name": "王志华", "age": 18, "addr": "北京"}
2 print('name' in stu_info) #判断key是否存在
3 print('name' in stu_info.keys())#判断key是否存在