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Comment by bombolo | Hacker News Reader

That's why in python that raises a KeyError, or if you use explicitly .get() you can specify anything as your default value.

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Which is why you end up with the painful

    sentinel = object()
    value = dictionary.get(key, sentinel)
    if(value == sentinel) ...

Which, sure, it works, but it's working around a problem that didn't need to exist in the first place. Why not just have Option work the way you expect, and be able to contain None the same way as it can contain any other value?

Well no, just handle KeyError :D

If you do that you still have the same problem, although the conditions for triggering it are narrower - you can't tell the difference between "your" KeyError and a KeyError from the callback you were passed.

It's probably subjective, but I don't see the need to wrap your code in a try/except block as an improvement over an optional sum type, and I really don't see the use of a magic value to indicate no value as an improvement over anything.

If it's not a try it's an if... you still need to handle the case where the key wasn't present and figure something out.

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