Forward values from JSON file as class attributes

Question

I have a settings file, which is loaded in once and takes the values from the settings json file and uses them as the attribute values. I was thinking of using the @property instead of overriding __getattribute__ but I feel as if there is a better, more elegant solution. Note that the application it is used in is multi-threaded.

settings.py

class SettingsMeta(type, JsonFileWrapperBase):
 _file_path = os.path.join(os.getcwd(), "..", "data", "settings.json")
 # Declarations to avoid PyCharm highlighting
 manga_save_dir, database_path, total_scrapper_threads, log_file = None, None, None, None
 _default_data = {
 "manga_save_dir": r"D:\dir",
 "database_path": r"D:\db.sqlite3",
 "log_file": os.path.join(os.getcwd(), "..", "data", "log.log"),
 "total_scrapper_threads": 1
 }
 @classmethod
 def __getattribute__(mcs, item):
 data = mcs._get_data()
 if item in data:
 return data[item]
 elif hasattr(mcs, item):
 return getattr(mcs, item)
 raise AttributeError(f"Settings has no attribute {item}")
class Settings(metaclass=SettingsMeta):
 pass

json_file_wrapper_base.py

class JsonFileWrapperBase:
 _loaded_data = None
 _file_path = ""
 _default_data = ""
 @classmethod
 def _write_default(cls):
 cls._write_data(cls._default_data)
 @classmethod
 def _write_data(cls, d):
 os.makedirs(os.path.dirname(os.path.abspath(cls._file_path)), exist_ok=True)
 try:
 with open(cls._file_path, "w") as f:
 json.dump(d, f)
 except FileNotFoundError as e:
 print(e)
 @classmethod
 def _get_data(cls):
 """
 Reads and caches the JSON file, if the file has already been cached then return the cached file, I cache
 the file to avoid users editing the file during execution and causing errors
 """
 # File has not been cached yet
 if cls._loaded_data is None:
 cls._read_file()
 return cls._loaded_data
 @classmethod
 def _read_file(cls) -> bool:
 assert cls._loaded_data is None, "_read_file should only be called once per object"
 # File doesn't exist or is not valid
 if not os.path.isfile(cls._file_path):
 cls._write_default()
 try:
 with open(cls._file_path, "r") as f:
 data = json.load(f)
 print(f"Log: Loaded {cls._file_path}")
 cls._loaded_data = data
 except FileNotFoundError as e:
 print(e)
 return False
 return True

• Graipher: Please add your imports. This is especially important since you use JsonFileWrapperBase._get_data.
• Joshua Nixon: I don't think the base class is relevant to my question about best practises forwarding values from JSON but I added it to my question neverthless.

Answer 1

Pathlib

Use it. It makes stuff like this:

os.path.join(os.getcwd(), "..", "data", "log.log"),

much nicer. It can also avoid this kind of thing:

"D:\dir"

namely, OS-specific directory separators. If you ever hope to have this be cross-platform, you'll want to remove your backslashes and use the libraries for path manipulation.

• Joshua Nixon: OK. First thing is that the base class is in a different file. i only added due to a comment (I'll make it clearer in my question). Second, the assert is a very last resort I used for debugging, It will never be called. Thirdly, as you can see I use a metaclass as solely overriding __getattribute__ doesn't work for which mcs is standard.
• Joshua Nixon: It was an formatting error regarding your assert comment. You haven't actually answered my question regarding forwarding values from JSON.
• Reinderien: That's true! And it doesn't matter - refer to codereview.meta.stackexchange.com/questions/5773/…
• Joshua Nixon: Ok, thats fair enough.