os.path.join - errors out

[DeaD_EyE]

Modern Python:

from pathlib import Path

data_path = Path('c:\\02')


for path in data_path.rglob("*"):
    if path.is_file():
        ...
    if path.is_dir():
        parent = path.parent
        name = path.name
        size_mib = path.stat().st_size / 1024**2
        if size_mib < 1:
            # skipping files with less than 1 MiB
            continue
        print(name, "->", size_mib)

The first party module pathlib has a better abstraction for paths.
So if you don't optimize to list 10_000_000 files, pathlib would do its job.

You should read this: https://realpython.com/python-pathlib/
The rglob is a recursive glob. It returns a generator and the generator yields Path objects. You can work with Path objects. For example you can get the parent (which is a dir, if the path was pointing to a file). You can get also the stat from files.