Python学习day7

一、静态方法

通过@staticmethod装饰器即可把其装饰的方法变为一个静态方法，什么是静态方法呢？其实不难理解，普通的方法，可以在实例化后直接调用，并且在方法里可以通过self.调用实例变量或类变量，但静态方法是不可以访问实例变量或类变量的，一个不能访问实例变量和类变量的方法，其实相当于跟类本身已经没什么关系了，它与类唯一的关联就是需要通过类名来调用这个方法

#Author:Fred

class Dog(object):
    def __init__(self,name):
        self.name = name
    @staticmethod #实际上和类没有关系了,不怎么用
    def eat(self):
        print("%s is eating %s"%(self.name,'dd'))
    
d = Dog("陈荣华")
d.eat(d)

 

二、类方法　　

类方法通过@classmethod装饰器实现，类方法和普通方法的区别是， 类方法只能访问类变量，不能访问实例变量

# Author:Fred

class Dog(object):
    name = "alex"
    def __init__(self, name):
        self.name = name

    @classmethod #类方法只能访问类变量，不能访问实例变量，不怎么用
    def eat(self):
        print("%s is eating %s" % (self.name, 'dd'))

    def talk(self):
        print("%s is talking"%self.name)


d = Dog("陈荣华")
d.eat()
#d.talk()

 

三、属性方法　　

属性方法的作用就是通过@property把一个方法变成一个静态属性

# Author:Fred

class Dog(object):
    '''这个类是描述狗这个对象的'''
    name = "alex"
    def __init__(self, name):
        self.name = name

    @property #属性方法，把一个方法变成一个静态属性
    def eat(self):
        print("%s is eating %s" % (self.name, 'dd'))

    @eat.setter
    def Eat(self, food):
        print("set to food:", food)

    def talk(self):
        print("%s is talking" % self.name)

    def __call__(self, *args, **kwargs):
        print("running call",args,kwargs)

    def __str__(self): #__str__ 如果一个类中定义了__str__方法，那么在打印 对象 时，默认输出该方法的返回值。
        return "<obj:%s>" %self.name

#print(Dog.__dict__)#字典形式打印类里的所有属性，不包括实例属性
#print(Dog.__doc__)
d = Dog("陈荣华")
print(d)
#print(d.__dict__)#字典形式打印类里的实例属性，不包括类属性
# d(1,2,3,name=333)
# d.eat #调用不能有参数了
# d.Eat = "baozi"

 

通过定义静态属性来实现的，比如，你想知道一个航班当前的状态，是到达了、延迟了、取消了、还是已经飞走了， 想知道这种状态你必须经历以下几步:

1. 连接航空公司API查询

2. 对查询结果进行解析 

3. 返回结果给你的用户

因此这个status属性的值是一系列动作后才得到的结果，所以你每次调用时，其实它都要经过一系列的动作才返回你结果，但这些动作过程不需要用户关心， 用户只需要调用这个属性就可以:

#Author:Fred
class Flight(object):
    def __init__(self,name):
        self.flight_name = name

    def checking_status(self):
        print("checking flight %s status " % self.flight_name)
        return 2

    @property
    def flight_status(self):
        status = self.checking_status()
        if status == 0:
            print("flight got canceled...")
        elif status == 1:
            print("flight is arrived...")
        elif status == 2:
            print("flight has departured already...")
        else:
            print("cannot confirm the flight status...,please check later")

    @flight_status.setter
    def flight_status(self,status):
        print("flight %s has changed status to %s" %(self.flight_name,status))

f = Flight("CA980")
f.flight_status
f.flight_status = 2

 

四、类的特殊成员方法

#Author:Fred
class MyType(type):
    def __init__(self,*args,**kwargs):
        print("Mytype __init__",*args,**kwargs)

    def __call__(self, *args, **kwargs):
        print("Mytype __call__", *args, **kwargs)
        obj = self.__new__(self)
        print("obj ",obj,*args, **kwargs)
        print(self)
        self.__init__(obj,*args, **kwargs)
        return obj

    def __new__(cls, *args, **kwargs):
        print("Mytype __new__",*args,**kwargs)
        return type.__new__(cls, *args, **kwargs)

print('here...')
class Foo(object,metaclass=MyType):

    def __init__(self,name):
        self.name = name

        print("Foo __init__")

    def __new__(cls, *args, **kwargs):
        print("Foo __new__",cls, *args, **kwargs)
        return object.__new__(cls)

f = Foo("Alex")
print("f",f)
print("fname",f.name)

 

五、反射

#Author:Fred
'''
hasattr(obj,name_str),判断一个对象obj里是否有对应的name_str字符串的方法
getattr(obj,name_str),根据字符串去获取obj对象里的对应的内存地址
setattr(obj,'y',z),相当于x.y = v
delattr()
'''
def bulk(self):
    print("%s is yelling..."%self.name)

class Dog(object):
    def __init__(self,name):
        self.name = name

    def eat(self,food):
        print("%s is eating..."%self.name,food)

d = Dog("Alex")
choice = input(">>:").strip()

if hasattr(d,choice): #判断有没有
    #delattr(d,choice)
    getattr(d,choice)
else:
    # setattr(d,choice,bulk)
    # d.bulk(d)
    setattr(d,choice,None)
    v = getattr(d,choice)#d.choice此时是一个字符串不能直接调用
    print(v)
print(d.name)

 

六、异常处理

1.#Author:Fred
names = ['alex','jack']
data = {}

try:
    # names[3]
    # data['name']
    open("tes.txt")
except KeyError as e:
    print("没有这个key",e)
except IndexError as e:
    print("列表操作错误",e)
except Exception as e:
    print("未知",e)
else:
    print("一切正常")
finally:
    print("不管有没有错都执行")

 

1. 自定义异常

#Author:Fred
class WupeiqiException(Exception):

    def __init__(self, msg):
        self.message = msg

    def __str__(self):
        return self.message

try:
    # name = []
    # name[3]
    raise WupeiqiException('我的异常') #触发
except WupeiqiException as e:
    print(e)

 

七、Socket 编程

1.socket_server.py：

#Author:Fred
import socket
server = socket.socket()
server.bind(('localhost',6969)) #绑定要监听的端口
server.listen() #监听

print("开始等电话")
conn,addr = server.accept() #等电话打进来
print(conn,addr) #coon就是客户端连过来而在服务器端为其生成的一个链接实例
print("电话打进来了")
while True:
    data = conn.recv(1024)
    print("recv:",data)
    conn.send(data.upper())

server.close()

 

2.socket_client.py：

#Author:Fred
import socket

client = socket.socket() #声明socket类型，同事生成socket连接对象
client.connect(('localhost',6969))

while True:
    msg = input(">>:").strip()
    if len(msg) == 0:continue
    client.send(msg.encode("utf-8"))
    data = client.recv(1024)
    print("recv:",data.decode())

client.close()