字典（dict ）
key-value，无序的(没有索引，通过键找值)、可变的数据类型(值可变，键不可变)
1).dict的格式
dic = {"name":"Jack","age":"23","height":"185","weight":"140"}
print(dic,type(dic))
2).dict的相关操作和函数
1).增：
通过键增加值
dic = {"name":"Jack","age":"23","height":"180","weight":"130"}
dic["job"] = "IT"
print(dic)
2).删：
pop(key) 删除指定key值的键值对，同时返回删除的值；
popitem() 删除字典中最后一对键值；
clear() 清空字典内元素,保留空字典
dic = {"name":"Jack","age":"23","weight":"130","height":"180"}
print(dic.pop("name"))
print(dic)
dic.popitem()
print(dic)
dic.clear()
print(dic)
3).改：
键改值
update(dic2) 将dic2中的键值对更新到dic中，键相同覆盖值，键不同直接增加键值对；
dic = {"name":"Jack","age":"23","weight":"130","height":"180"}
dic["name"] = "alex"
print(dic)
dic2 = {"name":"Alex","job":"IT"}
dic.update(dic2)
print(dic)
4).查：
键找值；
get("key") 返回key所对应的值，字典中无key值，则报错；
setdefault("key") 类似get，字典中如果无key值，会自动添加一个None值作为新的键值对添加到字典中；
keys() 得到所以的key值；
values() 得到所以的value值；
items() 将key和value放入元组中；
formkeys(seq,[value]) 生成一个新的字典，所以键只对应同一个值，seq--新字典的键，value--新字典的值；
dic = {"name":"Jack","age":"23","weight":"130","height":"180"}
print(dic["name"])
print(dic.get("name"))
print(dic.setdefault("job"))
print(dic)
print(dic.keys())
print(dic.values())
print(dic.items())
seq = ("name","age","job")
dict = dict.fromkeys(seq,["Jack",23])
print(dict)
5).对字典整体的操作：
copy() 复制字典
del() 删除整个字典
dic = {"name":"Jack","age":"23","weight":"130","height":"180"}
dic2 = dic.copy()
print(dic2)
del dic2
print(dic2)