定义一个字典
{key1:value1,key2:value2}
info = {"name":"laowang","old":18}
添加元素
info = {"name":"laowang","old":18}
info["old"] = 18 #info = {"name":"laowang","old":18}
修改元素
info = {"name":"laowang","old":18}
info["old"] = 20 #{"name":"laowang","old":20}
删除元素
info = {"name":"laowang","old":18}
del info["old"] #{"name":"laowang"}
查询元素
info = {"name":"laowang","old":18}
info.get("name") #laowang
info.get("qq") # 空
info["qq"] #抛出异常
常用属性
len 键值对的个数
info = {"name":"laowang","old":18}
info.len() # 打印信息2
keys 字典中所有的键列表
info = {"name":"laowang","old":18}
info.keys() # 打印信息["name","old"]
values 字典中所有的值列表
info = {"name":"laowang","old":18}
info.values() # 打印信息["laowang",18]
items 字典中所有的键值元组列表
info = {"name":"laowang","old":18}
info.items() # 打印信息[("name","laowang"),("old",18)]
字典中的key不能是列表类型，可以是字符串、数字、元组
