When importing a file using importlib the id() of the object being imported is not the same as when imported using the `import` keyword. I feel like this is a bug. As if I have a package which is using relative imports, and then I import all of the files in that package via importlib. issubclass and isinstance and others no longer work when the relative imported object and then importlib imported object are checked against each other, I assume because the id()s are different.

$ cat > target.py <<'EOF'
class Target:
    pass

EOF

$ cat > importer.py <<'EOF'
import importlib
from target import Target

spec = importlib.util.spec_from_file_location("target", "target.py")
imported_by_importlib = importlib.util.module_from_spec(spec)
spec.loader.exec_module(imported_by_importlib)

print("isinstance(imported_by_importlib.Target(), Target:",
isinstance(imported_by_importlib.Target(), Target))
print("id(Target):", id(Target))
print("id(imported_by_importlib.Target):", id(imported_by_importlib.Target))

EOF

$ python importer.py
isinstance(imported_by_importlib.Target(), Target: False
id(Target): 93824998820112
id(imported_by_importlib.Target): 93824998821056

That's expected because you are constructing a completely new module object with importlib.util.module_from_spec(). You're also completely circumventing sys.modules with the code you wrote which is the only way you would get equivalent IDs compared to using the import statement.

So this is working as intended.

Thank you! :) I must have missed that somehow