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Comment by ghshephard | Hacker News Reader

I love the walrus operator - and use it quite a bit, but, replacing

       if hi is None:
          hi = len(a)

With:

       hi ??= len(a)

Just sounds gratuitous. I'm happy this was deferred.

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It's actually simpler then that

    hi = len(a) if hi is None else hi

Your `if-else` is more complex than the original that just uses `if`.

The line itself is longer, but the idiom in the original uses mutation, which requires reading more adjacent lines to understand and make sure you haven't missed anything.

(In the concrete example, both versions use mutation.)

I'm not sure I understand. Could you give a concrete example where only one version uses mutation?

Any example that does what the proposed ??= operator does, which is inherently conditional mutation, will use mutation.

You can get examples equivalent to the proposed None-coalescing ?? operator does that don't use mutation, though.

There's a major difference though: `value if predicate else alternative` is itself a value, something you can assign to a variable or pass to a function as a parameter.

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