python - 如何使用 python 装饰器修复 "NoneType"错误？

Question

这个问题已经有答案了:

Decorator error: NoneType object is not callable (4 个回答)

已关闭 5 个月前。

我正在使用装饰器进行 LRU(最近最少使用)缓存来存储最近使用的本地化，但是当我调用函数从 .json 文件读取它时，我收到“NoneType”错误

def loc_cache(func):
    loc_cache.locale = {} # {lang:(local, count)} local:dict
    loc_cache.MAXLENGTH = 5
    def wrapper(key):
        print(key) #this function wasn't called
        if key not in loc_cache.locale.keys():
            try:
                locale = read_locale(key)
                loc_cache.locale[key] = (locale, 1)
                wrapper.locale = locale
            except KeyError:
                key = "en" # set default locale
                wrapper(key)
        else:
            locale, count = loc_cache.locale[key]
            loc_cache.locale[key] = (locale, count+1)
            wrapper.locale = locale
        return wrapper.locale

@loc_cache
def read_locale(key):
    locale = read_json("./config/locale.json", key)
    return locale

def auth(user:User):
    locale = read_locale(user.locale)
    print(locale["auth"])
    return

u = User(1) # __init__ takes 1 for id
u.locale = "en"
auth(u)

我希望它会返回存储在 .json 文件中的“en”中的短语，但它说

Traceback (most recent call last):
  File "main.py", line 61, in <module>
    auth(u)
  File "main.py", line 52, in auth
    locale = read_locale(user.locale)
TypeError: 'NoneType' object is not callable

Answer 1

您没有从装饰器返回包装函数，因此 Python 像往常一样返回 None 并在您执行 read_locale(user.locale) 时尝试调用它。您需要:

def loc_cache(func):
    loc_cache.locale = {} # {lang:(local, count)} local:dict
    loc_cache.MAXLENGTH = 5
    def wrapper(key):
        print(key) #this function wasn't called
        if key not in loc_cache.locale.keys():
            try:
                locale = read_locale(key)
                loc_cache.locale[key] = (locale, 1)
                wrapper.locale = locale
            except KeyError:
                key = "en" # set default locale
                wrapper(key)
        else:
            locale, count = loc_cache.locale[key]
            loc_cache.locale[key] = (locale, count+1)
            wrapper.locale = locale
        return wrapper.locale
    return wrapper
    # Here ^^^^