aosabook/500lines · error · ValueError

Database closed.

Error message

Database closed.

What it means

Error "Database closed." thrown in aosabook/500lines.

Source

Thrown at data-store/code/dbdb/interface.py:13

from dbdb.binary_tree import BinaryTree
from dbdb.physical import Storage


class DBDB(object):

    def __init__(self, f):
        self._storage = Storage(f)
        self._tree = BinaryTree(self._storage)

    def _assert_not_closed(self):
        if self._storage.closed:
            raise ValueError('Database closed.')

    def close(self):
        self._storage.close()

    def commit(self):
        self._assert_not_closed()
        self._tree.commit()

    def __getitem__(self, key):
        self._assert_not_closed()
        return self._tree.get(key)

    def __setitem__(self, key, value):
        self._assert_not_closed()
        return self._tree.set(key, value)

    def __delitem__(self, key):
        self._assert_not_closed()

View on GitHub (pinned to fba689d101)

Solutions

1. Do not call get/set/commit/delete after calling db.close().
2. Reopen the database with dbdb.connect(path) to continue using it.
3. Use a context manager (with dbdb.connect(...) as db) so close happens after all operations.

Example fix

db = dbdb.connect('data.db'); db.commit(); db.close(); db = dbdb.connect('data.db')  # reopen instead of using the closed handle

When it happens

Trigger: Thrown at data-store/code/dbdb/interface.py:13 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of aosabook/500lines@fba689d101 (2026-08-13). Data as JSON: /api/errors/65f186c32f2f2198. Report an issue: GitHub.