1、 静态方法staticmethod
只是名义上归类管理,实际上再静态方法里访问不了类和实例中的任何属性
定义:
通过@staticmethod装饰器即可以把其装饰的方法变为一个静态方法,普通的方法可以在实例化之后直接调用,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。
如果按照之前学习的面向对象,写一个简单的代码如下:
1 class Dog(object):
2 def __init__(self,name):
3 self.name = name
4
5 def eat(self,food):
6 print("%s is eating %s" %(self.name,food))
7
8 d =Dog("小A")
9 d.eat("包子")
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法1.py
2 小A is eating 包子
3
4 Process finished with exit code 0
接着对代码进行修改
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 @staticmethod
6 def eat(self,food):
7 print("%s is eating %s" %(self.name,food))
8
9
10 d = Dog("小A")
11 d.eat("包子")
运行结果:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 Traceback (most recent call last):
3 File "D:/python培训/s14/day7/静态方法.py", line 14, in <module>
4 d.eat("包子")
5 TypeError: eat() missing 1 required positional argument: 'food'
6
7 Process finished with exit code 1
出现了如上述的错误,为了避免food参数的问题,我们再次将代码进行修改:
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 @staticmethod
6 def eat(self):
7 print("%s is eating %s" %(self.name,"包子"))
8
9
10 d = Dog("小A")
11 d.eat()
但是运行结果仍然出现如下错误:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 Traceback (most recent call last):
3 File "D:/python培训/s14/day7/静态方法.py", line 14, in <module>
4 d.eat()
5 TypeError: eat() missing 1 required positional argument: 'self'
6
7 Process finished with exit code 1
其实这就是静态方法,这个时候eat函数和类其实没有上面关系,也可以说静态方法阶段了函数和类的关系
我们再次将代码进行更改:
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 @staticmethod
6 def eat():
7 print("%s is eating %s" %("小A","包子"))
8
9
10 d = Dog("小A")
11 d.eat()
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 小A is eating 包子
3
4 Process finished with exit code 0
如果非要传入参数可以将代码更改为,但是下面的代码意义不是特别大:
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 @staticmethod
6 def eat(self):
7 print("%s is eating %s" %(self.name,"包子"))
8
9
10 d = Dog("小A")
11 d.eat(d)
运行结果也是正常的
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 小A is eating 包子
3
4 Process finished with exit code 0
2、 类方法classmethod
类方法只能访问类变量,不能访问实例变量
我们先写如下代码
1 #AUTHOR:FAN
2 class Dog(object):
3 def __init__(self,name):
4 self.name = name
5 @classmethod
6 def eat(self):
7 print("%s is eating %s" %(self.name,"包子"))
8 d = Dog("dean")
9 d.eat()
运行结果出现如下错误:
1 D:\python35\python.exe D:/python培训/s14/day7/类方法2.py
2 Traceback (most recent call last):
3 File "D:/python培训/s14/day7/类方法2.py", line 15, in <module>
4 d.eat()
5 File "D:/python培训/s14/day7/类方法2.py", line 7, in eat
6 print("%s is eating %s" %(self.name,"包子"))
7 AttributeError: type object 'Dog' has no attribute 'name'
8
9 Process finished with exit code 1
上述显示无法调用到name
将代码进行修改
1 class Dog(object):
2 name = "AAA"
3 def __init__(self,name):
4 self.name = name
5 @classmethod
6 def eat(self):
7 print("%s is eating %s" %(self.name,"包子"))
8 d = Dog("dean")
9 d.eat()
运行效果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/类方法2.py
2 AAA is eating 包子
3
4 Process finished with exit code 0
从上面的运行结果可以看出虽然我实例化的时候传入了dean但是确实类变量AAA
3、属性方法property
将一个方法变成一个静态属性
我们先写如下代码:
1 class Dog(object):
2 def __init__(self,name):
3 self.name = name
4 @property
5 def eat(self):
6 print("%s is eating %s" %(self.name,"包子"))
7 d = Dog("dean")
8 d.eat()
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/属性方法2.py
2 dean is eating 包子
3 Traceback (most recent call last):
4 File "D:/python培训/s14/day7/属性方法2.py", line 9, in <module>
5 d.eat()
6 TypeError: 'NoneType' object is not callable
7
8 Process finished with exit code 1
所以我将代码进行修改(将d.eat()改为d.eat):
1 #AUTHOR:FAN
2 class Dog(object):
3 def __init__(self,name):
4 self.name = name
5 @property
6 def eat(self):
7 print("%s is eating %s" %(self.name,"包子"))
8 d = Dog("dean")
9 d.eat
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/属性方法2.py
2 dean is eating 包子
3
4 Process finished with exit code 0
从上面可以看出将一个方法变成一个静态属性
但是这个时候也同样发现无法传参数了。并且及时是已经是一个静态属性了,也是不能赋值的
如果想要赋值,可以将代码进行如下修改:
1 class Dog(object):
2 def __init__(self,name):
3 self.name = name
4 self.__food = None
5 @property
6 def eat(self):
7 print("%s is eating %s" %(self.name,self.__food))
8 @eat.setter
9 def eat(self,food):
10 print("set to food:",food)
11 self.__food = "包子"
12 d = Dog("dean")
13 d.eat
14 d.eat="包子" d.eat
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/属性方法2.py
2 dean is eating None
3 set to food: 包子
4 dean is eating 包子
5
6 Process finished with exit code 0
这样通过上面的方法就可以对其作为属性进行赋值修改
但是默认情况下属性方法是无法删除的,如果想要删除,需要:
1 #AUTHOR:FAN
2 class Dog(object):
3 def __init__(self,name):
4 self.name = name
5 self.__food = None
6 @property
7 def eat(self):
8 print("%s is eating %s" %(self.name,self.__food))
9 @eat.setter
10 def eat(self,food):
11 print("set to food:",food)
12 self.__food = "包子"
13 @eat.deleter
14 def eat(self):
15 del self.__food
16 print("删完了")
17
18 d = Dog("dean")
19 d.eat
20 d.eat="包子"
21 d.eat
22 del d.eat
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/属性方法2.py
2 dean is eating None
3 set to food: 包子
4 dean is eating 包子
5 删完了
6
7 Process finished with exit code 0
4、 类的特殊成员方法
__doc__表示类的描述信息
__module__表示当前操作的对象在哪个模块
__class__表示当前操作的对象的类是什么
__init__构造方法,通过类创建对象时,自动触发执行
__del__ 析构函数,当对象在内存中释放时,自动触发执行
__call__对象后面加括号,触发执行
代码例子:
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 # @staticmethod
6 def eat(self,food):
7 print("%s is eating %s" %(self.name,food))
8 def __call__(self, *args, **kwargs):
9 print("running call",args,kwargs)
10
11
12 d = Dog("小A")
13 d(1,2,3,4,name="dean")
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 running call (1, 2, 3, 4) {'name': 'dean'}
3
4 Process finished with exit code 0
__dict__查看类或对象中的所有成员
代码例子:
1 class Dog(object):
2
3 def __init__(self,name):
4 self.name = name
5 # @staticmethod
6 def eat(self,food):
7 print("%s is eating %s" %(self.name,food))
8 def __call__(self, *args, **kwargs):
9 print("running call",args,kwargs)
10
11
12 d = Dog("小A")
13 # d(1,2,3,4,name="dean")
14 print(Dog.__dict__)
15 print(d.__dict__)
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/静态方法.py
2 {'__doc__': None, 'eat': <function Dog.eat at 0x0000000000B6E378>, '__init__': <function Dog.__init__ at 0x0000000000B6E2F0>, '__weakref__': <attribute '__weakref__' of 'Dog' objects>, '__call__': <function Dog.__call__ at 0x0000000000B6E400>, '__dict__': <attribute '__dict__' of 'Dog' objects>, '__module__': '__main__'}
3 {'name': '小A'}
4 Process finished with exit code 0
从上面例子也可以看出print(Dog.__dict__)打印类里的所有属性,不包括实例属性
print(d.__dict__)打印所有实例属性,不包括类属性
__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
__getitem__ __setitem__ __telitem__
用于索引操作,如字典。以上分别表示获取,设置、删除数据
__new__
代码如下:
1 class Foo(object):
2 def __init__(self,name):
3 self.name = name
4
5 f = Foo("dean")
6 print(type(f))
7
8 print((type(Foo)))
在上述代码中f是通过Foo实例化的对象,其实不仅f是一个对象,Foo类本身也是一个对象,因为在python中一切事物都是对象
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/__new__.py
2 <class '__main__.Foo'>
3 <class 'type'>
4
5 Process finished with exit code 0
上面的输出同样表示了:
<class ‘__main__.Foo’>表示f对象由Foo类创建
<class 'type'> 表示Foo类对象由type类创建
所以从上面也可以得出f对象时Foo类的一个实例,Foo类对象时type类的一个实例,即Foo类对象时通过type类构造方法创建的
所以创建类就可以有两种方法:
普通方法
1 class Foo(object):
2 def func(self):
3 print("hello dean")
特殊方法
1 def func(self):
2 print("hello dean")
3 Foo = type('Foo',(object,),{'talk':func})
4 f = Foo()
5 f.talk()
6 print(type(Foo))
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/__new__.py
2 hello dean
3 <class 'type'>
4
5 Process finished with exit code 0
从这里也可以看出type就是类的类,所有的类都是通过type创建的
将上述代码进行修改:
1 def func(self):
2 print("hello dean")
3
4 def __init(self ,name,age):
5 self.name = name
6 self.age = age
7 Foo = type('Foo',(object,),{'talk':func,
8 '__init__':__init})
9 f = Foo("dean",23)
10 print(f.name)
11 print(f.age)
12 f.talk()
13 print(type(Foo))
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/__new__.py
2 dean
3 23
4 hello dean
5 <class 'type'>
6
7 Process finished with exit code 0
5、 反射
getattr(obj,name_str)判断一个对象obj里是否有对应name_str的字符串的方法映射
getattr(obj,name_str) 根据字符串去获取obj对象里的对应的方法的内存地址
代码例子:
1 class Dog(object):
2 def __init__(self,name):
3 self.name = name
4
5 def eat(self):
6 print("%s is eating..." %self.name)
7
8
9 d = Dog("dean")
10 choice = input(">>>:").strip()
11 #
12 # print(hasattr(d,choice))
13 # print(getattr(d,choice))
14 #
15 # getattr(d,choice)()
16 if hasattr(d,choice):
17 func = getattr(d,choice)
18 func()
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/反射1.py
2 >>>:eat
3 dean is eating...
4
5 Process finished with exit code 0
如果输入的字符串对应的方法不存在的情况让添加外面的类:代码如下,
1 def bulk(self):
2 print("%s is yelling....." %self.name)
3
4 class Dog(object):
5 def __init__(self,name):
6 self.name = name
7
8 def eat(self):
9 print("%s is eating..." %self.name)
10
11
12 d = Dog("dean")
13 choice = input(">>>:").strip()
14
15 if hasattr(d,choice):
16 func = getattr(d,choice)
17 func()
18 else:
19 setattr(d,choice,bulk)
20 d.talk(d)
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/反射1.py
2 >>>:talk
3 dean is yelling.....
4
5 Process finished with exit code 0
setattr(obj,’y’,z) 相当于x.y = v
代码例子:
1 if hasattr(d,choice):
2 func = getattr(d,choice)
3 func()
4 else:
5 setattr(d,choice,22)
6 print(getattr(d,choice))
删除是delattr(d,choice)
6、异常处理
语法:
1 try:
2 pass
3 except Exception as e:
4 pass
一个简单的例子:
1 name =[1,2,3]
2
3 try:
4 name[4]
5 except IndexError as e:
6 print(e)
如果想要同时抓多个错误的方法:
1 try:
2 code
3 except(Error1,Error2) as e:
4 print(e)
如果想要一次性抓住所有错误可以用Exceptions(一般不用,无法定位错误,但是一般放到最后面,用于提示未知错误):
1 name =[1,2,3]
2
3 try:
4 name[4]
5 except Exceptions e:
6 print(e)
else 表示一切正常
finally 表示不管有没有错都执行
一些常见的异常:
1 AttributeError 试图访问一个对象没有的树形,比如foo.x,但是foo没有属性x
2 IOError 输入/输出异常;基本上是无法打开文件
3 ImportError 无法引入模块或包;基本上是路径问题或名称错误
4 IndentationError 语法错误(的子类) ;代码没有正确对齐
5 IndexError 下标索引超出序列边界,比如当x只有三个元素,却试图访问x[5]
6 KeyError 试图访问字典里不存在的键
7 KeyboardInterrupt Ctrl+C被按下
8 NameError 使用一个还未被赋予对象的变量
9 SyntaxError Python代码非法,代码不能编译(个人认为这是语法错误,写错了)
10 TypeError 传入对象类型与要求的不符合
11 UnboundLocalError 试图访问一个还未被设置的局部变量,基本上是由于另有一个同名的全局变量,
12 导致你以为正在访问它
13 ValueError 传入一个调用者不期望的值,即使值的类型是正确的
自定义异常代码例子:
1 class myerror(Exception):
2 def __init__(self, msg):
3 self.message = msg
4
5 try:
6 name = []
7 name = [3]
8 raise myerror('我的异常')
9 except myerror as e:
10 print(e)
运行结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/自定义异常.py
2 我的异常
3
4 Process finished with exit code 0
7、 socket编程
一个简单的例子:
服务端:
1 import socket
2 server = socket.socket()
3 server.bind(('127.0.0.1',6969)) #绑定要监听的端口
4 server.listen()#监听
5
6 print("我要开始等电话了")
7 #conn就是客户端连过来而在服务器端为其生成的一个连接实例
8 conn,addr = server.accept()#等待电话打来
9
10 print("电话来了")
11
12 data = conn.recv(1024)
13 print("recv:",data)
14 conn.send(data.upper())
15
16 server.close()
客户端:
1 import socket
2
3 client = socket.socket()
4 client.connect(('127.0.0.1',6969))
5
6 client.send(b"Hello world")
7 data = client.recv(1204)
8 print("recv:",data)
9
10 client.close()
先运行服务端,在运行客户端,结果如下:
1 D:\python35\python.exe D:/python培训/s14/day7/socket_server1.py
2 我要开始等电话了
3 电话来了
4 recv: b'Hello world'
5
6 Process finished with exit code 0
7 D:\python35\python.exe D:/python培训/s14/day7/socket_client1.py
8 recv: b'HELLO WORLD'
9
10 Process finished with exit code 0
将上述代码进行改进:
服务端:
1 import socket
2 server = socket.socket()
3 server.bind(('127.0.0.1',6969)) #绑定要监听的端口
4 server.listen()#监听
5
6 print("我要开始等电话了")
7 while True:
8 # conn就是客户端连过来而在服务器端为其生成的一个连接实例
9 conn, addr = server.accept() # 等待电话打来
10 print("电话来了")
11 while True:
12 data = conn.recv(1024)
13 print("recv:",data)
14 if not data:
15 print("client has lost....")
16 break
17 conn.send(data.upper())
18 server.close()
客户端:
1 import socket
2
3 client = socket.socket()
4 client.connect(('127.0.0.1',6969))
5 while True:
6 msg = input(">>:").strip()
7 client.send(msg.encode("utf-8"))
8 data = client.recv(1204)
9 print("recv:",data.decode())
10
11 client.close()
上述代码改进后可以在客户端断开后,服务端不会进入死循环没如果这个时候有新的客户端进入,可以继续通讯