python 装饰器用法

# 装饰器的用法

# 1.一个简单的类型检查

def require_int(decorated):

    def inner(*args,**kwargs):

        kwargs_values = [i for i in kwargs.values()]

        for a in (kwargs_values + list(args)):

            if not isinstance(a,int):
                raise TypeError('%s only accept interger as  argument' % decorated.__name__)

        return decorated(*args,**kwargs)
    return inner

@require_int
def foo(x,y):
    "sum of x and y"
    return x+y



re = foo(1,2)
# print(re)
# print(help(foo))

#2.帮助保存信息***************************************************************


import functools

def require_int(decorated):
    @functools.wraps(decorated)
    def inner(*args,**kwargs):

        kwargs_values = [i for i in kwargs.values()]

        for a in (kwargs_values + list(args)):

            if not isinstance(a,int):
                raise TypeError('%s only accept interger as  argument' % decorated.__name__)

        return decorated(*args,**kwargs)
    return inner

@require_int
def foo(x,y):
    "sum of x and y"
    return x+y


re = foo(1,2)
# print(re)
# print(help(foo))

#3.用户验证***************************************************************

class User(object):

    def __init__(self,username,email):
        self.username = username
        self.email = email

class anonymousUser(User):

    def __init__(self):
        self.username = None
        self.email = None

    def __nonzero__(self):
        return False

def requires_user(decorated):
    @functools.wraps(decorated)
    def inner(user,*args,**kwargs):
        if user and isinstance(user,User):
            return decorated(user,*args,**kwargs)
        else:
            raise ValueError('a valid user is required to run this')

    return inner


#3.输出格式化***************************************************************

class JSONOutputError(Exception):
    def __init__(self,message):
        self._message = message

    def __str__(self):
        return self._message

import json
def json_output(decorted):
    @functools.wraps(decorted)
    def inner(*args,**kwargs):
        try:
            result = decorted(*args,**kwargs)
            if result:
                return json.dumps(result)
        except JSONOutputError as e:
            return json.dumps(
                {
                    'status':'error',
                    'message':str(e)
                }
            )

    return inner

@json_output
def do_nothing():
    return {'status':'done'}

@json_output
def error():
    raise JSONOutputError('this function is erratic')

print(error())

#4.日志管理***************************************************************

import time
import logging

def logged(decorated):
    @functools.wraps(decorated)
    def inner(*args,**kwargs):

        start = time.time()
        re_value = decorated(*args,**kwargs)
        end = time.time()
        delt = end - start
        logger = logging.getLogger('decorated.logged')
        logger.info('%s was called ,spennd time %f,result is %s' %(decorated.__name__,delt,re_value))

        return re_value
    return inner

@logged
def sleep(return_value):

    time.sleep(2)
    return return_value

print(sleep(8))

#4.向后兼容的装饰器***************************************************************

def json_output(decorated_= None,indent = None,sort_keys = False):

    def actual_decorator(func):
        @functools.wraps(func)
        def inner(*args,**kwargs):
            try:
                result = func(*args, **kwargs)
                if result:
                    return json.dumps(result,indent=indent,sort_keys=sort_keys)
            except JSONOutputError as e:
                return json.dumps(
                    {
                        'status': 'error',
                        'message': str(e)
                    },indent=indent,sort_keys=sort_keys
                )

        return inner

    if decorated_:
        return actual_decorator(decorated_)
    else:
        return actual_decorator

#4.类型转换（celery应用）***************************************************************

class Task(object):

    def run(self):

        raise NotImplementedError('subclasses must implement run')

    def identify(self):
        return 'i am a task'

def task(decorated):
    """将函数转换成类的装饰器"""
    class TaskSubclass(Task):
        def run(self,*args,**kwargs):
            return decorated(*args,**kwargs)

    return TaskSubclass

@task
def foo():
    return 2+2

print(foo().run())
print(foo().identify())


#5.类型转换调用升级（celery应用）***************************************************************
class TaskUpdate(object):

    def run(self):

        raise NotImplementedError('subclasses must implement run')

    def identify(self):
        return 'i am a task'

    def __call__(self, *args, **kwargs):
        return self.run(*args, **kwargs)

def task(decorated):
    """将函数转换成类的装饰器"""
    class TaskSubclass(TaskUpdate):
        def run(self,*args,**kwargs):
            return decorated(*args,**kwargs)

    return TaskSubclass()

@task
def foo():
    return 2+2

print(foo())
print(foo.identify())