A few days ago I posted Late initialization with mypy, and people gave me feedback, and I realized they were right. The placebo solution described there is clever, but too clever. It circumvents the value of static type checking.

The comments on the blog post were telling me this, but what helped most was a Mastodon thread with Glyph, especially when he said:

I am using “correct” to say “type-time semantics consistently matching runtime semantics.”

The placebo works to say “there’s always a thing,” but it’s not a real thing. A more useful and clearer solution is to admit that sometimes there isn’t a thing, and to be explicit about that.

I actually took a slightly middle-ground approach. Some of the “sometimes” attributes already had null implementations I could use, but I removed all of the explicit “Placebo” classes.