How to check if a font has been modified?

[ftCLI]

When performing operations on fonts, is there a simple way to detect if a font has been modified?

for f in files:

    font = ttLib.TTFont("font.ttf")

    font["OS/2"].usWeightClass = 300

    if font.modified == True:
        font.save(f)
    else:
        print("No changes made.")

I'd like to avoid saving a font if hasn't been modified (in the example, if usWeightClass value was already 300 the font must not be saved)

[anthrotype]

No, that's not possible, unless we were to add some magic that intercepts setattr, setitem, etc. throughout the lib to watch for any changes (which I think would be overkill).

[anthrotype]

in an ideal world, we would use immutable types everywhere and any change would entail creating a new object (similar to dataclasses.replace or attrs.evolve for frozen classes), but that's also hard to do at this stage. It'd mean a complete rewrite, given how most fonttools stuff relies on object mutability