yt-dlp/devscripts/lazy_load_template.py

import importlib
import random
import re

from ..utils import (
    age_restricted,
    bug_reports_message,
    classproperty,
    write_string,
)

# These bloat the lazy_extractors, so allow them to passthrough silently
ALLOWED_CLASSMETHODS = {'extract_from_webpage', 'get_testcases', 'get_webpage_testcases'}
_WARNED = False


class LazyLoadMetaClass(type):
    def __getattr__(cls, name):
        global _WARNED
        if ('_real_class' not in cls.__dict__
                and name not in ALLOWED_CLASSMETHODS and not _WARNED):
            _WARNED = True
            write_string('WARNING: Falling back to normal extractor since lazy extractor '
                         f'{cls.__name__} does not have attribute {name}{bug_reports_message()}\n')
        return getattr(cls.real_class, name)


class LazyLoadExtractor(metaclass=LazyLoadMetaClass):
    @classproperty
    def real_class(cls):
        if '_real_class' not in cls.__dict__:
            cls._real_class = getattr(importlib.import_module(cls._module), cls.__name__)
        return cls._real_class

    def __new__(cls, *args, **kwargs):
        instance = cls.real_class.__new__(cls.real_class)
        instance.__init__(*args, **kwargs)
        return instance