[IshKebab]

I think if you feel like you need this then it's a bit of a red flag and you should be using Pydantic or `dataclass` instead, then your IDE can statically tell you which fields you don't access (among many other benefits). Dicts are mainly for when you don't know the keys up front.

[mb7733]

Static analysis could only tell you which fields are never used, across all usage of the class. Not on a given instance.

[taeric]

Counterpoint, something like this for dataclasses would also be very useful.

That is, it isn't just knowing whether or not the data is ever used. It is useful to know if it was used in this specific run. And often times, seeing what parts of the data was not used is a good clue as to what went wrong. At the least, you can use it to rule out what code was not hit.