第6章 字典

Posted 2021-03-12 dingdangsunny

字典用花括号创建

message = {‘name‘: ‘dida‘, ‘age‘: "19"}
print(message[‘age‘])

字典是一系列键-值对，可以通过键访问与之相关联的值
与键相关联的值可以是任意类型的对象

message[‘height‘] = 176#添加新的对象
del message[‘height‘]#删除字典中的对象

遍历字典

message = {‘name‘:‘dida‘, ‘age‘: "19"}
for key, value in message.items():
print("
Key:" +key)
print("Value:" +value)

输出
Key:name
Value:dida

Key:age
Value:19
for循环依次将每个键-值对存储到制定的两个变量中
这两个变量可以使用任何名称

注意！便利字典时，键-值对的返回顺序不一定与存储顺序相同
Python不关心键-值对的存储顺序，而只跟踪键与值之间的关联关系
如需排序需要使用sorted()函数

message = {‘name‘:‘dida‘, ‘age‘: "19"}
for key in message.keys():#.keys用于提取键
#for key in message:
print("Key:" +key)
for value in message.values():#.values用于提取值
print("Value:" + value)

set()函数用于创建集合，集合中的元素互不相同，可用于去重

favorite_languages = {‘jen‘:‘python‘,
‘sarah‘: ‘C‘,
‘edward‘: ‘ruby‘,
‘phil‘: ‘python‘}
print("The following languages have been mentioned")
for value in favorite_languages.values():
print(value.title())
print("
The following languages have been mentioned")
for value in set(favorite_languages.values()):
print(value.title())

输出
The following languages have been mentioned
Python
C
Ruby
Python

The following languages have been mentioned
Ruby
C
Python

嵌套
python可以在列表中嵌套字典，在字典中嵌套列表，在字典中嵌套字典

users = {
‘aeinstein‘: {
‘first‘: ‘albert‘,
‘last‘: ‘einstein‘,
‘location‘: ‘princeton‘,
},
‘mcurie‘: {
‘first‘: ‘marie‘,
‘last‘: ‘curie‘,
‘location‘: ‘paris‘,
},
}
for username,user_info in users.items():
print("
Username:" + username)
full_name = user_info[‘first‘] + " " + user_info[‘last‘]
location = user_info[‘location‘]

print("	Full name: " + full_name.title())
print("	Location: " + location.title())

输出
Username:aeinstein
Full name: Albert Einstein
Location: Princeton

Username:mcurie
Full name: Marie Curie
Location: Paris