Is there a function that I can call that takes a Book ID as input and returns the generic filename of the book, (i.e. no extension), without the full library path?

construct_path_name() and construct_file_name()

construct_file_name() returned exactly what I expected but construct_path_name() returned a folder path relative to the library. Is there anyway to return the full OS path to the library folder?

For example: C:\Folders\Books\Main\Dickens, Charles\The Pickwick Papers (168)

db.library_path

Thanks, that completes the set!

All 3 of these work without me adding any extra import statements to the plugin.
How do I know when an import is required or not? Do I just try first without and see if it fails?

For example, in the same plugin I have "from calibre.ebooks.metadata.meta import get_metadata" and this one is necessary for use of get_metadata.

import statements add names to the current namespace. If the name is already present, like db then you dont need to import it.