字典：
字典取值快，通过key去找
字典是无序的，因为其不是按照顺序进行取值的，是按照key和value进行取值的
1、定义
info={} #定义空字典
info={"name":"zhaozhao","age":23,"sex":"男"} #定义字典
2、增加KEY
增加KEY两种方式：
info["key"]=value # 字典该KEY存在改变其值，不存该KEY则增加该KEY
info.setdefault(key,value) #字典该KEY存在不改变其值，不存该KEY则增加该KEY
info={"name":"zhaozhao"}
info["sex"]=23
info["name"]="zhaozhao1"
print(info)
D:studypython estvenvScriptspython.exe D:/study/python/test/dd.py {'name': 'zhaozhao1', 'sex': 23}
info={"name":"zhaozhao"}
info.setdefault("sex","男")
info.setdefault("name","zhaozhao2")
print(info)
D:studypython estvenvScriptspython.exe D:/study/python/test/dd.py
{'name': 'zhaozhao', 'sex': '男'}
3、删除
pop：指定key删除，key不存在会报错
del：指定key删除，key不存在会报错
popitem：随机返回并删除字典中的一对键和值。 如果字典已经为空，却调用了此方法，就报出KeyError异常
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
info.pop("name")
print("pop:",info)
del info["sex"]
print("del:",info)
info.popitem()
print("popitem:",info)
pop: {'sex': '男', 'age': '10', '班级': '1班', '成绩': '90'}
del: {'age': '10', '班级': '1班', '成绩': '90'}
popitem: {'age': '10', '班级': '1班'}
4、字典取值
如果key存在，2者没有什么区别，如果key不存在，info["key"]这种方式程序报错，info.get("phone")这种方式返回none
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
print(info["name"])
print(info.get('name'))
print("=========================")
print(info.get('ab'))
print(info["ab"])
5、获取key集合，获取value集合
print(info.keys()) #获取字典所有的key
print(info.values()) #获取字典所有的value
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
print(info.keys())
print(info.values())
D:studypython estvenvScriptspython.exe D:/study/python/test/dd.py
dict_keys(['name', 'sex', 'age', '班级', '成绩'])
dict_values(['zhaozhao', '男', '10', '1班', '90'])
6、判断key是否存在于字典
info.haskey("key") #python2
key in info #python3用于这种方式判断key是否存在于字典
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
cname='name'
dname='zhaozhao'
#key是否在key集合中
if cname in info.keys():
print("sucess")
#value是否在values集合中
if dname in info.values():
print("sucess2")
#key是否在字典中
if cname in info:
print("sucess3")
7、一个字典追加另一个字典
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
info2={"score":"89"}
info.update(info2)
print(info)
D:studypython estvenvScriptspython.exe D:/study/python/test/dd.py
{'name': 'zhaozhao', 'sex': '男', 'age': '10', '班级': '1班', '成绩': '90', 'score': '89'}
8、循环字典值
info={"name":"zhaozhao","sex":"男","age":"10","班级":"1班","成绩":"90"}
for k in info:
print("%s => %s"%(k,info[k]))
for k,v in info.items():
print("%s => %s"%(k,v))
这两种第一种性能上说快一些，第二种性能弱一些