Dictionary字典常用于存储键值对的集合。它是无序的、可修改的并且不允许重复。字典用{}表示，有k/v个键值对，比如下面定义的字典结构。thisdict={"brand":"Ford","model":"Mustang","year":1964}print(thisdict)PSE:\dream\markdown\python>&"C:/ProgramFiles(x86)/Python/python.exe"e:/dream/markdown/python/app/app.py{'brand':'Ford','model':'Mustang','year':1964}DictionaryItems字典中的项目都是key-value的形式，通常我们使用key来获取字典的内容，如下代码所示：thisdict={"brand":"Ford","model":"Mustang","year":1964}print(thisdict["brand"])PSE:\dream\markdown\python>&"C:/ProgramFiles(x86)/Python/python.exe"e:/dream/markdown/python/app/app.pyFordUnordered,modifiable当我们说字典是无序的，就是说它没有预先定义的顺序，不可能通过index方法获取到字典中的item。字典是可修改的，这意味着我们可以修改、添加和删除创建的字典中的项目。不允许重复，这意味着同一个键不可能有两个项目。可能有朋友会问，添加新项时遇到重复key怎么办？在python中，默认会覆盖之前的同名key，如下代码所示：thisdict={"brand":"Ford","model":"Mustang","year":1964,"year":2020}print(thisdict)PSE:\dream\markdown\python>&"C:/ProgramFiles(x86)/Python/python.exe"e:/dream/markdown/python/app/app.py{'brand':'Ford','model':'Mustang','year':2020}Dictionarylength判断字典中有多少条目，可以使用len()方法，比如下面的代码：thisdict={"brand":"Ford","model":"Mustang","year":1964,"year":2020}print(len(thisdict))PSE:\dream\markdown\python>&"C:/ProgramFiles(x86)/Python/python.exe"e:/dream/markdown/python/app/app.py3字典项的数据类型字典项的value值可以是任意类型，比如int、字符串、数组等，如下代码所示：thisdict={"brand":"Ford","electric":False,"year":1964,"colors":["red","white","blue"]}type()本质上，一个dict就是一个类dict的类，如下代码所示：thisdict={"brand":"Ford","model":"Mustang","year":1964}print(type(thisdict))PSE:\dream\markdown\python>&"C:/程序Files(x86)/Python/python.exe"e:/dream/markdown/python/app/app.py
