Python Decorator装饰器

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1. 基本装饰器

1.1. 无参方法无参装饰器

# 无参log装饰器def log(func):    def wrapper():        print('Log: excute method {}()'.format(func.__name__))        return func()    return wrapper# 无参方法@logdef do_save():    print('save something!')# Log: excute method do_save()# save something!do_save()

1.2. 有参方法无参装饰器

利用(*args, **kwargs)来表示任意参数。
此时若@log则会出现异常，因为@log装饰器的实现中并没有接收参数。

# 无参装饰器def log_new(func):    def wrapper(*args, **kwargs):        print('Log: excute method {}()'.format(func.__name__))        return func(*args, **kwargs)    return wrapper# 带参数的方法# @log  # TypeError need 1 argument@log_newdef do_save_user(user):    print('save {}'.format(user))# Log: excute method do_save_user()# save JiangWdo_save_user('JiangW')

1.3. 有参方法有参装饰器

# 带参数的装饰器def log_level(level):    def decorator(func):        def wrapper(*args, **kwargs):            print('Log[{}]: excute method {}()'.format(level, func.__name__))            return func(*args, **kwargs)        return wrapper    return decorator@log_level('INFO')def do_delete_user(user):    print('delete {}'.format(user))# Log[INFO]: excute method do_delete_user()# delete JiangWdo_delete_user('JiangW')

2. 基于类实现的装饰器

2.1. 简单基于类实现的装饰器

# 带参数class LoggingLevel(object):    def __init__(self, level):        self.level = level    def __call__(self, func):        def wrapper(*args, **kwargs):            print('Log[{}]: excute method {}()'.format(self.level, func.__name__))            return func(*args, **kwargs)        return wrapper@LoggingLevel('WARN')def do_remove_user(user):    print('remove {}'.format(user))# Log[WARN]: excute method do_remove_user()# remove JiangWdo_remove_user('JiangW')

3. 注意事项

3.1. 拆分装饰器

利用@log_level语法糖来实现的装饰器。

def log_level(level):    def decorator(func):        def wrapper(*args, **kwargs):            print('Log[{}]: excute method {}()'.format(level, func.__name__))            return func(*args, **kwargs)        return wrapper    return decorator@log_level('INFO')def do_delete_user(user):    print('delete {}'.format(user))# Log[INFO]: excute method do_delete_user()# delete JiangWdo_delete_user('JiangW')

拆分成每一步实际上最终为:

# 等同于def do_delete_user(user):    print('delete {}'.format(user))# # Log[INFO]: excute method do_delete_user()# delete JiangWdecorator = log_level('INFO')wrapper = decorator(do_delete_user)wrapper('Jian111gW')

3.2. 函数名称改变

如3.1所述拆分装饰器后实际上最终是调用了

wrapper = decorator(do_delete_user)wrapper('Jian111gW')

此时被@log_level装饰器装饰的函数名已经变成了wrapper

print(do_delete_user.__name__)  # wrapper

利用functools.wraps来修正

def log_level(level):    def decorator(func):        @wraps(func)        def wrapper(*args, **kwargs):            print('Log[{}]: excute method {}()'.format(level, func.__name__))            return func(*args, **kwargs)        return wrapper    return decorator@log_level('INFO')def do_delete_user(user):    print('delete {}'.format(user))print(do_delete_user.__name__)  # do_delete_user

此时do_delete_user.__name__为do_delete_user.

4. 使用wrapt和decoractor

4.1. wrapt

4.2. decoractor

5. 延伸

5.1. 内置装饰器

5.2. 另类用法

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