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Is there a way to register a file so that it is deleted when Python exits, regardless of how it exits? I am using long-lived temporary files and want to ensure they are cleaned up.

The file must have a filename and it's original handle should be closed as soon as possible -- there will be thousands of these created and I need to ensure they exist only as normal files.

Answers

Use the tempfile module; it creates temporary files that auto-delete.

From the tempfile.NamedTemporaryFile() documentation:

If delete is true (the default), the file is deleted as soon as it is closed.

You can use such a file object as a context manager to have it closed automatically when the code block exits, or you leave it to be closed when the interpreter exits.

The alternative is to create a dedicated temporary directory, with tempdir.mkdtemp(), and use shutil.rmtree() to delete the whole directory when your program completes.

Preferably, you do the latter with another context manager:

import shutil
import sys
import tempfile

from contextlib import contextmanager


@contextmanager
def tempdir():
    path = tempfile.mkdtemp()
    try:
        yield path
    finally:
        try:
            shutil.rmtree(path)
        except IOError:
            sys.stderr.write('Failed to clean up temp dir {}'.format(path))

and use this as:

with tempdir() as base_dir:
    # main program storing new files in base_dir

# directory cleaned up here

You could do this with a atexit hook function, but a context manager is a much cleaner approach.