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  • python之反射

    isinstance和issubclass

    isinstance(obj,cls)检查是否obj是否是类 cls 的对象

    class Foo:
    pass
class Son(Foo):
    pass
s=Son()

print(isinstance(s,Son))

    issubclass(sub, super)检查sub类是否是 super 类的派生类 

    class Foo(object):
    pass
 
class Bar(Foo):
    pass
 
issubclass(Bar, Foo)

    反射

    python面向对象中的反射：通过字符串的形式操作对象相关的属性，python中一切事物都是对象（都可以用反射）

    下列方法适用于类和对象：

     检查是否含有某属性---hasattr 返回布尔值
    获取属性---getattr   没有就会报错
    设置属性---setattr
    删除属性---delattr
    class Foo:
    f = '类的静态变量'
    def __init__(self,name,age):
        self.name=name
        self.age=age

    def say_hi(self):
        print('hi,%s'%self.name)

obj=Foo('egon',73)

#检测是否含有某属性
print(hasattr(obj,'name'))
print(hasattr(obj,'say_hi'))

#获取属性
n=getattr(obj,'name')
print(n)
func=getattr(obj,'say_hi')
func()

print(getattr(obj,'aaaaaaaa','不存在啊')) #报错

#设置属性
setattr(obj,'sb',True)
setattr(obj,'show_name',lambda self:self.name+'sb')
print(obj.__dict__)
print(obj.show_name(obj))

#删除属性
delattr(obj,'age')
delattr(obj,'show_name')
delattr(obj,'show_name111')#不存在,则报错

print(obj.__dict__)
    四个方法的使用
    

    

    

    class Foo(object):
 
    staticField = "old boy"
 
    def __init__(self):
        self.name = 'agg'
 
    def func(self):
        return 'func'
 
    @staticmethod
    def bar():
        return 'bar'
 
print getattr(Foo, 'staticField')
print getattr(Foo, 'func')
print getattr(Foo, 'bar')
    

    
类也是属性
    

    导入其他模块
    

    

    

    import my_module
def demo1():
    print('demo1')
print(hasattr(demo1,'demo1'))
    

    
没在同一个文件下找模块
    

    

    

    def demo1():
    print('demo1')
import sys
module_obj=sys.modules[__name__]
print(hasattr(module_obj,'demo1'))
getattr(module_obj,'demo1')
    

    
在一个文件下找模块
    

    改对象的字符串显示__str__和__repr__:
    

    %s和%r
    

    __del__
    


    

    

    class Foo:
    def __del__(self):
        print('fgs')
f=Foo()
print(123)
print(123)
del f
print(123)
print(123)
print(123)
    

    
del示范
    


    item系列
    


    __getitem__\__setitem__\__delitem__
    

    

    

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

    def __getitem__(self, item):
        print(self.__dict__[item])

    def __setitem__(self, key, value):
        self.__dict__[key]=value
    def __delitem__(self, key):
        print('del obj[key]时,我执行')
        self.__dict__.pop(key)
    def __delattr__(self, item):
        print('del obj.key时,我执行')
        self.__dict__.pop(item)

f1=Foo('sb')
f1['age']=18
f1['age1']=19
del f1.age1
del f1['age']
f1['name']='alex'
print(f1.__dict__)
    

    
View Code
    

    __new__
    

    

    

    class A:
    def __init__(self):  #有一个方法在帮你创造self
        print('in init function')
        self.x=1
    def __new__(cls, *args, **kwargs):
        print('in init funct')
        return object.__new__(A,*args,**kwargs)
a=A()
    

    
View Code
    

    单例模式
    


    

    

    class Singleton:
    def __new__(cls, *args, **kw):
        if not hasattr(cls, '_instance'):
            orig = super(Singleton, cls)
            cls._instance = orig.__new__(cls, *args, **kw)
        return cls._instance

one = Singleton()
two = Singleton()

two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)
    

    
View Code
    


    

    

    class Foo:

    def __init__(self):
        pass
    
    def __call__(self, *args, **kwargs):

        print('__call__')


obj = Foo() # 执行 __init__
obj()       # 执行 __call__
    

    
__call__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __len__(self):
        return len(self.__dict__)
a = A()
print(len(a))
    

    
__len__模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __hash__(self):
        return hash(str(self.a)+str(self.b))
a = A()
print(hash(a))
    

    
__hash__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __eq__(self,obj):
        if  self.a == obj.a and self.b == obj.b:
            return True
a = A()
b = A()
print(a == b)
    

    
__eq__ 模式
    

    

    

    class Person:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __hash__(self):
        return hash(self.name+self.sex)

    def __eq__(self, other):
        if self.name == other.name and self.sex == other.sex:return True


p_lst = []
for i in range(84):
    p_lst.append(Person('egon',i,'male'))

print(p_lst)
print(set(p_lst))
    

    
面试题
    





     
    


    ---恢复内容结束---
    

    isinstance和issubclass
    

    isinstance(obj,cls)检查是否obj是否是类 cls 的对象
    

    

    class Foo:
    pass
class Son(Foo):
    pass
s=Son()

print(isinstance(s,Son))
    

    


    issubclass(sub, super)检查sub类是否是 super 类的派生类 
    


    

    class Foo(object):
    pass
 
class Bar(Foo):
    pass
 
issubclass(Bar, Foo)
    

    


    反射
    

    python面向对象中的反射：通过字符串的形式操作对象相关的属性，python中一切事物都是对象（都可以用反射）
    

    下列方法适用于类和对象：
    


     检查是否含有某属性---hasattr 返回布尔值
    获取属性---getattr   没有就会报错
    设置属性---setattr
    删除属性---delattr
    

    

    

    class Foo:
    f = '类的静态变量'
    def __init__(self,name,age):
        self.name=name
        self.age=age

    def say_hi(self):
        print('hi,%s'%self.name)

obj=Foo('egon',73)

#检测是否含有某属性
print(hasattr(obj,'name'))
print(hasattr(obj,'say_hi'))

#获取属性
n=getattr(obj,'name')
print(n)
func=getattr(obj,'say_hi')
func()

print(getattr(obj,'aaaaaaaa','不存在啊')) #报错

#设置属性
setattr(obj,'sb',True)
setattr(obj,'show_name',lambda self:self.name+'sb')
print(obj.__dict__)
print(obj.show_name(obj))

#删除属性
delattr(obj,'age')
delattr(obj,'show_name')
delattr(obj,'show_name111')#不存在,则报错

print(obj.__dict__)
    

    
四个方法的使用
    

    

    

    

    class Foo(object):
 
    staticField = "old boy"
 
    def __init__(self):
        self.name = 'agg'
 
    def func(self):
        return 'func'
 
    @staticmethod
    def bar():
        return 'bar'
 
print getattr(Foo, 'staticField')
print getattr(Foo, 'func')
print getattr(Foo, 'bar')
    

    
类也是属性
    

    导入其他模块
    

    

    

    import my_module
def demo1():
    print('demo1')
print(hasattr(demo1,'demo1'))
    

    
没在同一个文件下找模块
    

    

    

    def demo1():
    print('demo1')
import sys
module_obj=sys.modules[__name__]
print(hasattr(module_obj,'demo1'))
getattr(module_obj,'demo1')
    

    
在一个文件下找模块
    

    改对象的字符串显示__str__和__repr__:
    

    %s和%r
    

    __del__
    


    

    

    class Foo:
    def __del__(self):
        print('fgs')
f=Foo()
print(123)
print(123)
del f
print(123)
print(123)
print(123)
    

    
del示范
    


    item系列
    


    __getitem__\__setitem__\__delitem__
    

    

    

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

    def __getitem__(self, item):
        print(self.__dict__[item])

    def __setitem__(self, key, value):
        self.__dict__[key]=value
    def __delitem__(self, key):
        print('del obj[key]时,我执行')
        self.__dict__.pop(key)
    def __delattr__(self, item):
        print('del obj.key时,我执行')
        self.__dict__.pop(item)

f1=Foo('sb')
f1['age']=18
f1['age1']=19
del f1.age1
del f1['age']
f1['name']='alex'
print(f1.__dict__)
    

    
View Code
    

    __new__
    

    

    

    class A:
    def __init__(self):  #有一个方法在帮你创造self
        print('in init function')
        self.x=1
    def __new__(cls, *args, **kwargs):
        print('in init funct')
        return object.__new__(A,*args,**kwargs)
a=A()
    

    
View Code
    

    单例模式
    


    

    

    class Singleton:
    def __new__(cls, *args, **kw):
        if not hasattr(cls, '_instance'):
            orig = super(Singleton, cls)
            cls._instance = orig.__new__(cls, *args, **kw)
        return cls._instance

one = Singleton()
two = Singleton()

two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)
    

    
View Code
    


    

    

    class Foo:

    def __init__(self):
        pass
    
    def __call__(self, *args, **kwargs):

        print('__call__')


obj = Foo() # 执行 __init__
obj()       # 执行 __call__
    

    
__call__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __len__(self):
        return len(self.__dict__)
a = A()
print(len(a))
    

    
__len__模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __hash__(self):
        return hash(str(self.a)+str(self.b))
a = A()
print(hash(a))
    

    
__hash__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __eq__(self,obj):
        if  self.a == obj.a and self.b == obj.b:
            return True
a = A()
b = A()
print(a == b)
    

    
__eq__ 模式
    

    

    

    class Person:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __hash__(self):
        return hash(self.name+self.sex)

    def __eq__(self, other):
        if self.name == other.name and self.sex == other.sex:return True


p_lst = []
for i in range(84):
    p_lst.append(Person('egon',i,'male'))

print(p_lst)
print(set(p_lst))
    

    
面试题
    





     
    


    ---恢复内容开始---
    

    isinstance和issubclass
    

    isinstance(obj,cls)检查是否obj是否是类 cls 的对象
    

    

    class Foo:
    pass
class Son(Foo):
    pass
s=Son()

print(isinstance(s,Son))
    

    


    issubclass(sub, super)检查sub类是否是 super 类的派生类 
    


    

    class Foo(object):
    pass
 
class Bar(Foo):
    pass
 
issubclass(Bar, Foo)
    

    


    反射
    

    python面向对象中的反射：通过字符串的形式操作对象相关的属性，python中一切事物都是对象（都可以用反射）
    

    下列方法适用于类和对象：
    


     检查是否含有某属性---hasattr 返回布尔值
    获取属性---getattr   没有就会报错
    设置属性---setattr
    删除属性---delattr
    

    

    

    class Foo:
    f = '类的静态变量'
    def __init__(self,name,age):
        self.name=name
        self.age=age

    def say_hi(self):
        print('hi,%s'%self.name)

obj=Foo('egon',73)

#检测是否含有某属性
print(hasattr(obj,'name'))
print(hasattr(obj,'say_hi'))

#获取属性
n=getattr(obj,'name')
print(n)
func=getattr(obj,'say_hi')
func()

print(getattr(obj,'aaaaaaaa','不存在啊')) #报错

#设置属性
setattr(obj,'sb',True)
setattr(obj,'show_name',lambda self:self.name+'sb')
print(obj.__dict__)
print(obj.show_name(obj))

#删除属性
delattr(obj,'age')
delattr(obj,'show_name')
delattr(obj,'show_name111')#不存在,则报错

print(obj.__dict__)
    

    
四个方法的使用
    

    

    

    

    class Foo(object):
 
    staticField = "old boy"
 
    def __init__(self):
        self.name = 'agg'
 
    def func(self):
        return 'func'
 
    @staticmethod
    def bar():
        return 'bar'
 
print getattr(Foo, 'staticField')
print getattr(Foo, 'func')
print getattr(Foo, 'bar')
    

    
类也是属性
    

    导入其他模块
    

    

    

    import my_module
def demo1():
    print('demo1')
print(hasattr(demo1,'demo1'))
    

    
没在同一个文件下找模块
    

    

    

    def demo1():
    print('demo1')
import sys
module_obj=sys.modules[__name__]
print(hasattr(module_obj,'demo1'))
getattr(module_obj,'demo1')
    

    
在一个文件下找模块
    

    改对象的字符串显示__str__和__repr__:
    

    %s和%r
    

    __del__
    


    

    

    class Foo:
    def __del__(self):
        print('fgs')
f=Foo()
print(123)
print(123)
del f
print(123)
print(123)
print(123)
    

    
del示范
    


    item系列
    


    __getitem__\__setitem__\__delitem__
    

    

    

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

    def __getitem__(self, item):
        print(self.__dict__[item])

    def __setitem__(self, key, value):
        self.__dict__[key]=value
    def __delitem__(self, key):
        print('del obj[key]时,我执行')
        self.__dict__.pop(key)
    def __delattr__(self, item):
        print('del obj.key时,我执行')
        self.__dict__.pop(item)

f1=Foo('sb')
f1['age']=18
f1['age1']=19
del f1.age1
del f1['age']
f1['name']='alex'
print(f1.__dict__)
    

    
View Code
    

    __new__
    

    

    

    class A:
    def __init__(self):  #有一个方法在帮你创造self
        print('in init function')
        self.x=1
    def __new__(cls, *args, **kwargs):
        print('in init funct')
        return object.__new__(A,*args,**kwargs)
a=A()
    

    
View Code
    

    单例模式
    


    

    

    class Singleton:
    def __new__(cls, *args, **kw):
        if not hasattr(cls, '_instance'):
            orig = super(Singleton, cls)
            cls._instance = orig.__new__(cls, *args, **kw)
        return cls._instance

one = Singleton()
two = Singleton()

two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)
    

    
View Code
    


    

    

    class Foo:

    def __init__(self):
        pass
    
    def __call__(self, *args, **kwargs):

        print('__call__')


obj = Foo() # 执行 __init__
obj()       # 执行 __call__
    

    
__call__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __len__(self):
        return len(self.__dict__)
a = A()
print(len(a))
    

    
__len__模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __hash__(self):
        return hash(str(self.a)+str(self.b))
a = A()
print(hash(a))
    

    
__hash__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __eq__(self,obj):
        if  self.a == obj.a and self.b == obj.b:
            return True
a = A()
b = A()
print(a == b)
    

    
__eq__ 模式
    

    

    

    class Person:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __hash__(self):
        return hash(self.name+self.sex)

    def __eq__(self, other):
        if self.name == other.name and self.sex == other.sex:return True


p_lst = []
for i in range(84):
    p_lst.append(Person('egon',i,'male'))

print(p_lst)
print(set(p_lst))
    

    
面试题
    





     
    


    ---恢复内容结束---
    

    isinstance和issubclass
    

    isinstance(obj,cls)检查是否obj是否是类 cls 的对象
    

    

    class Foo:
    pass
class Son(Foo):
    pass
s=Son()

print(isinstance(s,Son))
    

    


    issubclass(sub, super)检查sub类是否是 super 类的派生类 
    


    

    class Foo(object):
    pass
 
class Bar(Foo):
    pass
 
issubclass(Bar, Foo)
    

    


    反射
    

    python面向对象中的反射：通过字符串的形式操作对象相关的属性，python中一切事物都是对象（都可以用反射）
    

    下列方法适用于类和对象：
    


     检查是否含有某属性---hasattr 返回布尔值
    获取属性---getattr   没有就会报错
    设置属性---setattr
    删除属性---delattr
    

    

    

    class Foo:
    f = '类的静态变量'
    def __init__(self,name,age):
        self.name=name
        self.age=age

    def say_hi(self):
        print('hi,%s'%self.name)

obj=Foo('egon',73)

#检测是否含有某属性
print(hasattr(obj,'name'))
print(hasattr(obj,'say_hi'))

#获取属性
n=getattr(obj,'name')
print(n)
func=getattr(obj,'say_hi')
func()

print(getattr(obj,'aaaaaaaa','不存在啊')) #报错

#设置属性
setattr(obj,'sb',True)
setattr(obj,'show_name',lambda self:self.name+'sb')
print(obj.__dict__)
print(obj.show_name(obj))

#删除属性
delattr(obj,'age')
delattr(obj,'show_name')
delattr(obj,'show_name111')#不存在,则报错

print(obj.__dict__)
    

    
四个方法的使用
    

    

    

    

    class Foo(object):
 
    staticField = "old boy"
 
    def __init__(self):
        self.name = 'agg'
 
    def func(self):
        return 'func'
 
    @staticmethod
    def bar():
        return 'bar'
 
print getattr(Foo, 'staticField')
print getattr(Foo, 'func')
print getattr(Foo, 'bar')
    

    
类也是属性
    

    导入其他模块
    

    

    

    import my_module
def demo1():
    print('demo1')
print(hasattr(demo1,'demo1'))
    

    
没在同一个文件下找模块
    

    

    

    def demo1():
    print('demo1')
import sys
module_obj=sys.modules[__name__]
print(hasattr(module_obj,'demo1'))
getattr(module_obj,'demo1')
    

    
在一个文件下找模块
    

    改对象的字符串显示__str__和__repr__:
    

    %s和%r
    

    __del__
    


    

    

    class Foo:
    def __del__(self):
        print('fgs')
f=Foo()
print(123)
print(123)
del f
print(123)
print(123)
print(123)
    

    
del示范
    


    item系列
    


    __getitem__\__setitem__\__delitem__
    

    

    

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

    def __getitem__(self, item):
        print(self.__dict__[item])

    def __setitem__(self, key, value):
        self.__dict__[key]=value
    def __delitem__(self, key):
        print('del obj[key]时,我执行')
        self.__dict__.pop(key)
    def __delattr__(self, item):
        print('del obj.key时,我执行')
        self.__dict__.pop(item)

f1=Foo('sb')
f1['age']=18
f1['age1']=19
del f1.age1
del f1['age']
f1['name']='alex'
print(f1.__dict__)
    

    
View Code
    

    __new__
    

    

    

    class A:
    def __init__(self):  #有一个方法在帮你创造self
        print('in init function')
        self.x=1
    def __new__(cls, *args, **kwargs):
        print('in init funct')
        return object.__new__(A,*args,**kwargs)
a=A()
    

    
View Code
    

    单例模式
    


    

    

    class Singleton:
    def __new__(cls, *args, **kw):
        if not hasattr(cls, '_instance'):
            orig = super(Singleton, cls)
            cls._instance = orig.__new__(cls, *args, **kw)
        return cls._instance

one = Singleton()
two = Singleton()

two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)
    

    
View Code
    


    

    

    class Foo:

    def __init__(self):
        pass
    
    def __call__(self, *args, **kwargs):

        print('__call__')


obj = Foo() # 执行 __init__
obj()       # 执行 __call__
    

    
__call__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __len__(self):
        return len(self.__dict__)
a = A()
print(len(a))
    

    
__len__模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __hash__(self):
        return hash(str(self.a)+str(self.b))
a = A()
print(hash(a))
    

    
__hash__ 模式
    

    

    

    class A:
    def __init__(self):
        self.a = 1
        self.b = 2

    def __eq__(self,obj):
        if  self.a == obj.a and self.b == obj.b:
            return True
a = A()
b = A()
print(a == b)
    

    
__eq__ 模式
    

    

    

    class Person:
    def __init__(self,name,age,sex):
        self.name = name
        self.age = age
        self.sex = sex

    def __hash__(self):
        return hash(self.name+self.sex)

    def __eq__(self, other):
        if self.name == other.name and self.sex == other.sex:return True


p_lst = []
for i in range(84):
    p_lst.append(Person('egon',i,'male'))

print(p_lst)
print(set(p_lst))
    

    
面试题
    


    
    
                
    
                
              
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                原文地址：https://www.cnblogs.com/mengqingjian/p/7374385.html
              
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