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[【原文链接】Python----Python高级特性-装饰器](http://devops-dev.com/article/140)

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# 一 装饰器是函数，
## 1.1 被装饰对象也是函数
装饰器是函数，被装饰对象是函数时，此时装饰器的作用是给被装饰对象的函数做功能增强功能，思想是面向切面编程思想，即在被装饰对象的函数的之前和之后做一些额外处理，而不破坏被装饰函数原有的功能实现，主要有以下几种情况：
### 1.1.1 装饰器无参数，被装饰对象无参数

```bash
def decorator(func):
    def _decorator():
        print("before func......")
        func()
        print("after func......")
    return _decorator

@decorator
def func():
    print("in func()......")

if __name__=="__main__":
    func()    
```

执行结果为：

```bash
before func......
in func()......
after func......
```

### 1.1.2 装饰器无参数，被装饰对象有参数

```bash
def decorator(func):
    def _decorator(*args,**kwargs):
        print("before {name}......".format(name=func.__name__))
        func(*args,**kwargs)
        print("after {name}......".format(name=func.__name__))
    return _decorator

@decorator
def func1():
    print("in func1()......")

@decorator
def func2(a,b):
    print("in func2()......")
    print("a={a},b={b}".format(a=a,b=b))

@decorator
def func3(a,b,c=10):
    print("in func3()......")
    print("a={a},b={b}".format(a=a, b=b))
    print("c={c}".format(c=c))

if __name__=="__main__":
    func1()
    func2(1,2)
    func3(1,2,c=100)
```

运行结果为：

```bash
before func1......
in func1()......
after func1......
before func2......
in func2()......
a=1,b=2
after func2......
before func3......
in func3()......
a=1,b=2
c=100
after func3......
```

### 1.1.3 装饰器有参数，被装饰对象无参数

```bash
def wrapper(name):
    def decorator(func):
        def _decorator():
            print("before {name} ,decorator param is {param}".format(name=func.__name__,param=name))
            print("before {name}......".format(name=func.__name__))
            func()
            print("after {name}......".format(name=func.__name__))
        return _decorator
    return decorator

@wrapper(name="hello world")
def func1():
    print("in func1()......")

if __name__=="__main__":
    func1()
```

运行结果为：

```bash
before func1 ,decorator param is hello world
before func1......
in func1()......
after func1......
```

### 1.1.4 装饰器有参数，被装饰器对象有参数

```bash
def wrapper(name):
    def decorator(func):
        def _decorator(*args,**kwargs):
            print("before {name} ,decorator param is {param}".format(name=func.__name__,param=name))
            print("before {name}......".format(name=func.__name__))
            func(*args,**kwargs)
            print("after {name}......".format(name=func.__name__))
        return _decorator
    return decorator

@wrapper(name="hello world")
def func1():
    print("in func1()......")

@wrapper(name="hello world")
def func2(a, b):
    print("in func2()......")
    print("a={a},b={b}".format(a=a, b=b))

@wrapper(name="hello world")
def func3(a, b, c=10):
    print("in func3()......")
    print("a={a},b={b}".format(a=a, b=b))
    print("c={c}".format(c=c))

if __name__=="__main__":
    func1()
    func2(1,2)
    func3(1,2,c=100)
```

运行结果如下：

```bash
before func1 ,decorator param is hello world
before func1......
in func1()......
after func1......
before func2 ,decorator param is hello world
before func2......
in func2()......
a=1,b=2
after func2......
before func3 ,decorator param is hello world
before func3......
in func3()......
a=1,b=2
c=100
after func3......
```

## 1.2 被装饰器对象是类

被装饰器对象为类时，装饰器的作用是类在初始化的时候做功能增强，即可以在类初始化之前或者之后做一些功能增强，所以下面所说的被装饰对象有无参数是针对类的初始化函数__init__有无参数而言的，主要有以下几种情况：

### 1.2.1 装饰器无参数，被装饰类无参数

```bash
def decorator(cls):
    def _decorator():
        print("before class {name} init......".format(name=cls.__name__))
        obj=cls()
        print("after class {name} init......".format(name=cls.__name__))
        return obj
    return _decorator

@decorator
class Test(object):
    def __init__(self):
        print("in class {name} init function......".format(name=Test.__name__))

def func(self):
        print("in class {name} func()".format(name=Test.__name__))

if __name__=="__main__":
    test=Test()
    
    test.func()
```

运行结果如下：

```bash
before class Test init......
in class _decorator init function......
after class Test init......
in class _decorator func()
```

### 1.2.2 装饰器无参数，被装饰类有参数

```bash
def decorator(cls):
    def _decorator(*args,**kwargs):
        print("before class {name} init......".format(name=cls.__name__))
        obj=cls(*args,**kwargs)
        print("after class {name} init......".format(name=cls.__name__))
        return obj
    return _decorator

@decorator
class Test(object):
    def __init__(self,a,b=10):
        print("in class {name} init function......".format(name=Test.__name__))
        print("a={a},b={b}".format(a=a,b=b))

def func(self):
        print("in class {name} func()".format(name=Test.__name__))

if __name__=="__main__":
    test=Test(2,20)
    
    test.func()
```

执行结果如下：

```bash
before class Test init......
in class _decorator init function......
a=2,b=20
after class Test init......
in class _decorator func()
```

### 1.2.3 装饰器有参数，被装饰类无参数

```bash
def wrapper(name="hello world"):
    def decorator(cls):
        def _decorator():
            print("before class {name} init......".format(name=cls.__name__))
            obj=cls()
            print("after class {name} init......".format(name=cls.__name__))
            return obj
        return _decorator
    return decorator

@wrapper("hello world")
class Test(object):
    def __init__(self):
        print("in class {name} init function......".format(name=Test.__name__))

def func(self):
        print("in class {name} func()".format(name=Test.__name__))

if __name__=="__main__":
    test=Test()
    
    test.func()
```

执行结果如下：

```bash
before class Test init......
in class _decorator init function......
after class Test init......
in class _decorator func()
```

### 1.2.4 装饰器有参数，被装饰类有参数

```bash
def wrapper(name="hello world"):
    def decorator(cls):
        def _decorator(*args,**kwargs):
            print("before class {name} init......".format(name=cls.__name__))
            obj=cls(*args,**kwargs)
            print("after class {name} init......".format(name=cls.__name__))
            return obj
        return _decorator
    return decorator

@wrapper("hello world")
class Test(object):
    def __init__(self,a,b=10):
        print("in class {name} init function......".format(name=Test.__name__))
        print("a= {a} b={b}".format(a=a,b=b))

def func(self):
        print("in class {name} func()".format(name=Test.__name__))

if __name__=="__main__":
    test=Test(2,b=20)
    
    test.func()
```

运行结果如下：

```bash
before class Test init......
in class _decorator init function......
a= 2 b=20
after class Test init......
in class _decorator func()
```

## 1.3 被装饰对象是类中的方法

当被装饰对象是类中的方法时，装饰器的作用是对类中的方法进行功能加强，此时需要注意的是装饰器的内层函数需要增加一个self形参

### 1.3.1 装饰器无参数，被装饰类中的方法无参数

```bash
def decorator(func):
    def _decorator(self):
        print("before method {name}......".format(name=func.__name__))
        obj = func(self)
        print("after method {name} ......".format(name=func.__name__))
        return obj

return _decorator

class Test(object):
    def __init__(self, a=1, b=10):
        self.a = a
        self.b = b

@decorator
    def func(self):
        print("in class {name} func()".format(name=Test.__name__))
        print("a={a} b={b}".format(a=self.a, b=self.b))

if __name__ == "__main__":
    test = Test()

test.func()
```

执行结果如下：

```bash
before method func......
in class Test func()
a=1 b=10
after method func ......
```

### 1.3.2 装饰器无参数，被装饰类中的方法有参数

```bash

def decorator(func):
    def _decorator(self,*args,**kwargs):
        print("before method {name} ......".format(name=func.__name__))
        obj=func(self,*args,**kwargs)
        print("after method {name} ......".format(name=func.__name__))
        return obj
    return _decorator

class Test(object):
    def __init__(self,a=1,b=10):
        self.a=a
        self.b=b
    @decorator
    def func(self,c,d=20):
        print("in class {name} func()".format(name=Test.__name__))
        print("a={a} b={b}".format(a=self.a,b=self.b))
        print("c={c} d={d}".format(c=c,d=d))

if __name__=="__main__":
    test=Test()

test.func(2,d=20)
```

执行结果如下：

```bash
before method func ......
in class Test func()
a=1 b=10
c=2 d=20
after method func ......

```

### 1.3.3 装饰器有参数，被装饰类中的方法无参数

```bash
def wrapper(name="hello world"):
    def decorator(func):
        def _decorator(self):
            print("before method {name} ......".format(name=func.__name__))
            print("name = {name}".format(name=name))
            obj=func(self)
            print("after method {name} ......".format(name=func.__name__))
            return obj
        return _decorator
    return decorator

class Test(object):
    def __init__(self,a=1,b=10):
        self.a=a
        self.b=b
    @wrapper(name="Test.func")
    def func(self):
        print("in class {name} func()".format(name=Test.__name__))
        print("a={a} b={b}".format(a=self.a,b=self.b))

if __name__=="__main__":
    test=Test()

test.func()
```

执行结果如下：

```bash
before method func ......
name = Test.func
in class Test func()
a=1 b=10
after method func ......
```

### 1.2.4 装饰器有参数，被装饰类中的方法有参数

```bash
def wrapper(name="hello world"):
    def decorator(func):
        def _decorator(self,*args,**kwargs):
            print("before metthod {name} ......".format(name=func.__name__))
            print("name = {name}".format(name=name))
            obj=func(self,*args,**kwargs)
            print("after method {name} ......".format(name=func.__name__))
            return obj
        return _decorator
    return decorator

class Test(object):
    def __init__(self,a=1,b=10):
        self.a=a
        self.b=b
    @wrapper(name="Test.func")
    def func(self,c,d=20):
        print("in class {name} func()".format(name=Test.__name__))
        print("a={a} b={b}".format(a=self.a,b=self.b))
        print("c={c} d={d}".format(c=c,d=d))

if __name__=="__main__":
    test=Test()

test.func(2,d=20)
```

执行结果如下：

```bash
before metthod func ......
name = Test.func
in class Test func()
a=1 b=10
c=2 d=20
after method func ......
```

# 二 装饰器是类

## 2.1 被装饰对象是函数

装饰器是类，被装饰对象是函数的时候，是通过装饰器类初始化的时候将被装饰对象函数传递给装饰器类，然后通过自动调用装饰器类中的__call__函数实现对被装饰对象的前后处理，即在这种情况下，只需要在__call__函数中编写在调用被装饰对象前后进行操作的代码即可

### 2.1.1 装饰器无参数，被装饰对象无参数

```bash
class decorator(object):
    def __init__(self,func):
        self.func=func

def __call__(self):
        print("before func {func}()...".format(func=self.func.__name__))
        result=self.func()
        print("after func {func}()...".format(func=self.func.__name__))
        return result

@decorator
def func():
    print("in func func()...")

if __name__=="__main__":
    func()
```

执行结果如下：

```bash
before func func()...
in func func()...
after func func()...
```

### 2.1.2 装饰器无参数，被装饰对象有参数

```bash
class decorator(object):
    def __init__(self,func):
        self.func=func

def __call__(self,*args,**kwargs):
        print("before func {func}()...".format(func=self.func.__name__))
        result=self.func(*args,**kwargs)
        print("after func {func}()...".format(func=self.func.__name__))
        return result

@decorator
def func(a,b=10):
    print("in func func()...")
    print("a= {a} b={b}".format(a=a,b=b))

if __name__=="__main__":
    func(2,b=20)
```

执行结果如下：

```bash
before func func()...
in func func()...
a= 2 b=20
after func func()...
```

### 2.1.3 装饰器有参数，被装饰对象无参数

```bash

class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,func):
        def wrapper():
            print("before func {func}()...".format(func=func.__name__))
            print("name= {name}".format(name=self.name))
            result=func()
            print("after func {func}()...".format(func=func.__name__))
            return result
        return wrapper

@decorator()
def func1():
    print("in func func2()...")

@decorator("func2_decorator")
def func2():
    print("in func func2()...")

@decorator(name="func3_decorator")
def func3():
    print("in func func3()...")

if __name__=="__main__":
    func1()
    
    func2()
    
    func3()
```

执行结果如下：

```bash
before func func1()...
name= hello world
in func func2()...
after func func1()...
before func func2()...
name= func2_decorator
in func func2()...
after func func2()...
before func func3()...
name= func3_decorator
in func func3()...
after func func3()...
```

### 2.1.4 装饰器有参数，被装饰器对象有参数

```bash

class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,func):
        def wrapper(*args,**kwargs):
            print("before func {func}()...".format(func=func.__name__))
            print("name= {name}".format(name=self.name))
            result=func(*args,**kwargs)
            print("after func {func}()...".format(func=func.__name__))
            return result
        return wrapper

@decorator()
def func1():
    print("in func func2()...")

@decorator("func2_decorator")
def func2(a):
    print("in func func2()...")
    print("a={a}".format(a=a))

@decorator(name="func3_decorator")
def func3(a,b=10):
    print("in func func3()...")
    print("a={a}, b= {b}".format(a=a,b=b))

if __name__=="__main__":
    func1()
    
    func2(10)
    
    func3(2,b=20)
```

执行结果如下：

```bash
before func func1()...
name= hello world
in func func2()...
after func func1()...
before func func2()...
name= func2_decorator
in func func2()...
a=10
after func func2()...
before func func3()...
name= func3_decorator
in func func3()...
a=2, b= 20
after func func3()...
```

## 2.2 被装饰器对象是类

同样，当被装饰对象是类是，装饰器的作用是对被装饰类的初始化方法进行功能加强，而装饰器则是以类的形式定义的

### 2.2.1 装饰器无参数，被装饰类无参数

```bash
class decorator(object):
    def __init__(self,cls):
        self.cls=cls

def __call__(self):
        print("before init clsss {cls}...".format(cls=self.cls.__name__))
        obj=self.cls()
        print("after init class {cls}...".format(cls=self.cls.__name__))
        return obj

@decorator
class Test():
    def __init__(self):
        print("in Test class __init__ func...")

def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test()
    t.test()
```

执行结果如下：

```bash
before init clsss Test...
in Test class __init__ func...
after init class Test...
in Test class test func...
```

### 2.2.2 装饰器无参数，被装饰类有参数

```bash
class decorator(object):
    def __init__(self,cls):
        self.cls=cls

def __call__(self,*args,**kwargs):
        print("before init clsss {cls}...".format(cls=self.cls.__name__))
        obj=self.cls(*args,**kwargs)
        print("after init class {cls}...".format(cls=self.cls.__name__))
        return obj

@decorator
class Test():
    def __init__(self,a,b=10):
        print("in Test class __init__ func...")
        print("a={a} b={b}".format(a=a,b=b))

def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test(2,b=20)
    t.test()
```

执行结果如下：

```bash
before init clsss Test...
in Test class __init__ func...
a=2 b=20
after init class Test...
in Test class test func...
```

### 2.2.3 装饰器有参数，被装饰类无参数

```bash
class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,cls):
        def wrapper():
            print("before init class {cls}....".format(cls=cls.__name__))
            obj=cls()
            print("after init class {cls}...".format(cls=cls.__name__))
            return obj
        return wrapper

@decorator(name="Test Class")
class Test():
    def __init__(self):
        print("in Test class __init__ func...")

def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test()
    t.test()
```

执行结果如下：

```bash
before init class Test....
in Test class __init__ func...
after init class Test...
in Test class test func...
```

### 2.2.4 装饰器有参数，被装饰类有参数

```bash
class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,cls):
        def wrapper(*args,**kwargs):
            print("before init class {cls}....".format(cls=cls.__name__))
            obj=cls(*args,**kwargs)
            print("after init class {cls}...".format(cls=cls.__name__))
            return obj
        return wrapper

@decorator(name="Test Class")
class Test():
    def __init__(self,a,b=10):
        print("in Test class __init__ func...")
        print("a={a}, b={b}".format(a=a,b=b))

def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test(2,b=20)
    t.test()
```

执行结果如下：

```bash
before init class Test....
in Test class __init__ func...
a=2, b=20
after init class Test...
in Test class test func...
```

## 2.3 被装饰对象是类中的方法

### 2.3.1 装饰器无参数，被装饰类中的方法无参数

```bash
class decorator(object):
    def __init__(self,func):
        self.func=func

def __call__(self):
        print("before func {func}...".format(func=self.func.__name__))
        results=self.func(self)
        print("after func {func}...".format(func=self.func.__name__))
        return results

class Test():
    def __init__(self):
        print("in Test class __init__ func...")

@decorator
    def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test()
    t.test()
```

执行结果如下：

```bash
in Test class __init__ func...
before func test...
in Test class test func...
after func test...
```

### 2.3.2 装饰器无参数，被装饰类中的方法有参数

```bash
class decorator(object):
    def __init__(self,func):
        self.func=func

def __call__(self,*args,**kwargs):
        print("before func {func}...".format(func=self.func.__name__))
        results=self.func(self,*args,**kwargs)
        print("after func {func}...".format(func=self.func.__name__))
        return results

class Test():
    def __init__(self):
        print("in Test class __init__ func...")

@decorator
    def test(self,a,b=10):
        print("in Test class test func...")
        print("a={a}  b={b}".format(a=a,b=b))

if __name__=="__main__":
    t=Test()
    t.test(2,b=20)
```

执行结果如下：

```bash
in Test class __init__ func...
before func test...
in Test class test func...
a=2  b=20
after func test...
```

### 2.3.3 装饰器有参数，被装饰类中的方法无参数

```bash
class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,func):
        def wrapper(self):
            print("before func {func}...".format(func=func.__name__))
            results=func(self)
            print("after func {func}...".format(func=func.__name__))
            return results
        return wrapper

class Test():
    def __init__(self):
        print("in Test class __init__ func...")

@decorator(name="Test_test")
    def test(self):
        print("in Test class test func...")

if __name__=="__main__":
    t=Test()
    t.test()
```

执行结果如下：

```bash
in Test class __init__ func...
before func test...
in Test class test func...
after func test...
```

### 2.3.4 装饰器有参数，被装饰类中的方法有参数

```bash
class decorator(object):
    def __init__(self,name="hello world"):
        self.name=name

def __call__(self,func):
        def wrapper(self,*args,**kwargs):
            print("before func {func}...".format(func=func.__name__))
            results=func(self,*args,**kwargs)
            print("after func {func}...".format(func=func.__name__))
            return results
        return wrapper

class Test():
    def __init__(self):
        print("in Test class __init__ func...")

@decorator(name="Test_test")
    def test(self,a,b=10):
        print("in Test class test func...")
        print("a={a}, b={b}".format(a=a,b=b))

if __name__=="__main__":
    t=Test()
    t.test(2,b=20)
```

执行结果如下：

```bash
in Test class __init__ func...
before func test...
in Test class test func...
a=2, b=20
after func test...
```

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