python7 静态方法、类方法、属性方法 ；反射；异常处理

#-*- coding:utf8 -*-
# 静态方法@staticmethod
# 静态方法（当eat变成静态方法后，再通过实例调用时就不会自动把实例本身当作一个参数传给self了。）
class Dog(object):
    def __init__(self, name):
        self.name = name
    #@staticmethod  # 静态方法（当eat变成静态方法后，再通过实例调用时就不会自动把实例本身当作一个参数传给self了。）
    def eat(self):
        print("%s is eating" % self.name)

d = Dog("ChenRonghua")
d.eat()
#报错信息
#TypeError: eat() missing 1 required positional argument: 'self'

# 类方法
# 类方法通过@classmethod装饰器实现，类方法只能访问类变量，不能访问实例变量
# （当eat变成静态方法后，再通过实例调用时就不会自动把实例本身当作一个参数传给self了。）
class Dog(object):
    def __init__(self, name):
        self.name = name
    @staticmethod
    def eat():
        print("%s is eating")#因为name是个实例变量，类方法是不能访问实例变量的

d = Dog("ChenRonghua")
d.eat()

class Dog(object):
    name = "我是类变量"

    def __init__(self, name):
        self.name = name
        self.__food=None

    @classmethod
    def eat(self):
        print("%s is eating" % self.name)
    def __call__(self, *args, **kwargs):#构造方法：对象=类名（） 而__call__ 则是：对象（）
        print("running call",args,kwargs)

    def __str__(self):
        return 'obj:%s'%self.name

d = Dog("ChenRonghua")
d(2,3,4,name='开发量')#__call__ 则是：对象（）
print(d.__dict__)#打印的是实例属性{'name': 'ChenRonghua', '_Dog__food': None}
print(Dog.__dict__)#打印的是类的属性
print(d)#module对象想知道它是谁__str__

d.eat()

#把一个类做成字典了

#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

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

    @property
    def eat(self):
        print(" %s is eating" % self.name)

d = Dog("ChenRonghua")
print (Dog.__doc__)

#d.eat() #因为eat此时已经变成一个静态属性了， 不是方法了， 想调用已经不需要加()号了，直接d.eat就可以了
d.eat

#@property 的实例---航班查询
#这个status属性的值是一系列动作后才得到的结果

class fly(object):
    def __init__(self,name):
        self._name=name
    def check_status(self):
        print("%s fly status"%self._name)
        return 2
    @property
    def fly_status(self):
        status=self.check_status()
        if status==0:
            print ("quxiao")
        elif status==1:
            print("daoda")
        elif status == 2:
            print("ready")
        else:
            print("later")
d=fly("k7")
d.fly_status

#-----------另一种
class fly(object):
    def __init__(self,name):
        self._name=name
    def check_status(self):
        print("%s fly status"%self._name)
        return 2
    def fly_status(self):
        status=self.check_status()
        if status==0:
            print ("quxiao")
        elif status==1:
            print("daoda")
        elif status == 2:
            print("ready")
        else:
            print("later")
d=fly("k7")
d.fly_status()

#__doc__表示类的描述信息
class Foo:
    """ 描述类信息，这是用于看片的神奇 """

    def func(self):
        pass

print(Foo.__doc__)

#__call__对象后面加括号
#构造方法，即：对象 = 类名() ；
#__call__方法 即：对象() 或者 类()()

class Foo:
    def __init__(self):
        print("__init__")

    def __call__(self, *args, **kwargs):
        print('__call__')

obj = Foo()  # 执行 __init__

obj()  # 执行 __call__

#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

class Foo:
    def __str__(self):
        return 'alex li'
obj = Foo()
print(obj)

#生命的起源是通过Type来实现的
def func(self):
    print ("hello %s"%self.name)

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

foo=type("foo",(object,),{"talk":func,
                           "__init__":__init__})
f =foo("alex",32)
f.talk()

print(type(foo)) #<class 'type'>

#-*- coding:utf8 -*-
class Dog():
    def __init__(self,name):
        self.name=name
    def eat(self):
        print ("%s is eating..."%self.name)

d=Dog("zhangsan")
choice=input(">>:").strip()
# print (hasattr(d,choice))#>>:eat---True
# getattr(d,choice)() #zhangsan is eating...
if hasattr(d,choice):
    func=getattr(d,choice)
    func()

#-*- coding:utf8 -*-
def dulk(self):
    print("%s is yelling.."%self.name)
class Dog():
    def __init__(self,name):
        self.name=name
    def eat(self,food):
        print ("%s is eating..."%self.name,food)

d=Dog("zhangsan")
choice=input(">>:").strip()
# print (hasattr(d,choice))#>>:eat---True
# getattr(d,choice)() #zhangsan is eating...
if hasattr(d,choice):
    func=getattr(d,choice)
    func("lisi") #>>:eat --zhangsan is eating... lisi
    #hasattr (obj,name_str)判断一个对象是否有对应的name_str字符串的
    #getattr(obj,name_str)根据字符串去获取对象对应方法里的内存地址
else :
    # setattr(d,choice,dulk)
    # d.talk(d)
    setattr(d,choice,32)
    print(getattr(d,choice)) #>>:talk --32

#-*- coding:utf8 -*-
def dulk(self):
    print("%s is yelling.."%self.name)
class Dog():
    def __init__(self,name):
        self.name=name
    def eat(self,food):
        print ("%s is eating..."%self.name,food)

d=Dog("zhangsan")
choice=input(">>:").strip()
# print (hasattr(d,choice))#>>:eat---True
# getattr(d,choice)() #zhangsan is eating...
if hasattr(d,choice):
    getattr(d,choice)
else :
   # print(setattr(d,choice,None))
    setattr(d,choice,dulk)
    func=getattr(d,choice)
    func(d)

#-*- coding:utf8 -*-
def dulk(self):
    print("%s is yelling.."%self.name)
class Dog():
    def __init__(self,name):
        self.name=name
    def eat(self,food):
        print ("%s is eating..."%self.name,food)

d=Dog("zhangsan")
choice=input(">>:").strip()
# print (hasattr(d,choice))#>>:eat---True
# getattr(d,choice)() #zhangsan is eating...
if hasattr(d,choice):
    func=getattr(d,choice)
    setattr(d ,choice,"xiaobai")
    # func("lisi") #>>:eat --zhangsan is eating... lisi
    #hasattr (obj,name_str)判断一个对象是否有对应的name_str字符串的
    #getattr(obj,name_str)根据字符串去获取对象对应方法里的内存地址
else :
    # setattr(d,choice,dulk)
    # d.talk(d)
    setattr(d,choice,32)
    print(getattr(d,choice))
print(d.name) #>>:name----xiaobai
#setattr (obj,'y',z) is equitvalent  to  x.y=z  对对象添加新的属性

异常处理

#-*- coding:utf8 -*-
#---字典出错,列表出错
data={}
names=['zhangsan','lisi']
# data['name'] #KeyError: 'name'
try:
    names[3] #这个报错，下一个错误就不会执行了
    data['name']

except KeyError as e:
    print('没有这个key',e)
except IndexError as e:
    print("列表操作错误", e)

try_未知错误-Exception最后用

data={}
names=['zhangsan','lisi']
# data['name'] #KeyError: 'name'
try:
    open("test.txt")
    names[3] # 如果它放在try的第一位 就不报未知错误
    data['name']

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: #错误排除不出来，最后报未知错误
    print ("未知错误",e )

ValueError

#-*- coding:utf8 -*-
s1="hello"
try:
    int(s1)
except  ValueError as e:
    print ("类型不正确",e)

两种错误都采用统一的处理办法

#-*- coding:utf8 -*-
#---字典出错,列表出错
data={}
names=['zhangsan','lisi']
# data['name'] #KeyError: 'name'
try:
    names[3] #这个报错，下一个错误就不会执行了
    data['name']

except (KeyError ,IndexError) as e:
    print('没有这个key',e)
# except IndexError as e:
#     print("列表操作错误", e)

自定义异常

#-*- coding:utf8 -*-
#__str__类返回什么格式
class flmException(Exception):
    def __init__(self,msg):
        self.message=msg
    # def __str__(self):
    #     return self.message #替换为 return "abc"
try:
    raise flmException("数据库连不上")
except flmException as e:
    print(e)