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Comment by never_inline | Hacker News Reader

Here's a use case - singleton instantiation on first request, where instantiation itself requires an async call (eg: to DB or external service).

    _lock = asyncio.Lock()
    _instance = None

    def get_singleton():
      if _instance:
        return _instance
      async with _lock:
        if not _instance:
          _instance = await costly_function()
      return _instance

How do you suggest to replace this?

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The traditional thing would be to have an init() function that is required to be called at the top of main() or before any other methods that need it. But I agree with your point.

Now lets say its an async cache instead of singleton.

Return the cached item if it exists else spawn a task to update it (doing nothing if the task has already been spawned), await the task and return the cached item.

Thanks, that's a useful trick.

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