Python,字典

字典是无序的，由（键-值）对组成，键，值之间用 （：）隔开，项之间用 （，）隔开，整个字典由（{ }）括起来。

1.创建字典

age={"wang":20,"zhong":20}

2.dict()--通过映射或者键-值对的序列 建立字典

item=[("name","wang"),("age",20)]d=dict(item)print(d){"name":"wang","age",20}

d=dict(name="wang",age=20)print(d){"name":"wang","age",20}

3.字典基本操作

message={"name":"wang","age":20}print("my name is %s(name)"% message)my name is wang

4.字典方法

clear()--清除字典所有项，原地操作，无返回值。

copy()--返回具有相同键值对新字典（浅复制，不是副本）

message={"name":"wang","age":20}other=message.copy()print(other){"name":"wang","age":20}

get()--访问字典项的方法

message={"name":"wang","age":20}print(message.get("name"))wang

has_key()--检查字典中是否含有特点键

message={"name":"wang","age":20}print(message.has_key("age"))true

items()和iteritens()--将字典所有项以列表方式返回，每一项都是一个键-值对

message={"name":"wang","age":20}print(message.items())[("name","wang"),("age",20)]

keys()和iterkeys()--将字典中的键以列表形式返回

pop()--移除字典中给定键的值，并返回该值

message={"name":"wang","age":20}print(message.pop("name"))"wang"

popitem()--类似于list.pop(),弹出字典中随机的项

message={"name":"wang","age":20}message.popitem()print(message){"name":"wang"}

setdefault()--类似于get(),此外，能在字典中不含给定键的情况下设定相应的键值

message={"name":"wang","age":20}print(message.setdefault("address"))Nullprint(message)message={"name":"wang","age":20,"address":Null}

update()--利用一个字典更新另外一个字典

message={"name":"wang","age":20}other={"address":"shaoyang","name":"zhong"}message.update(other)print(message)message={"name":"zhong","age":20,"address":"shaoyang"}

values()和itervalues()--以列表的形式返回字典中的值

message={"name":"wang","age":20}print(message.values())["wang",20]