{"id": "internals:database-execute-write-fn", "page": "internals", "ref": "database-execute-write-fn", "title": "await db.execute_write_fn(fn, block=True, transaction=True)", "content": "This method works like  .execute_write() , but instead of a SQL statement you give it a callable Python function. Your function will be queued up and then called when the write connection is available, passing that connection as the argument to the function. \n                 The function can then perform multiple actions, safe in the knowledge that it has exclusive access to the single writable connection for as long as it is executing. \n                 \n                     fn  needs to be a regular function, not an  async def  function. \n                 \n                 For example: \n                 def delete_and_return_count(conn):\n    conn.execute(\"delete from some_table where id > 5\")\n    return conn.execute(\n        \"select count(*) from some_table\"\n    ).fetchone()[0]\n\n\ntry:\n    num_rows_left = await database.execute_write_fn(\n        delete_and_return_count\n    )\nexcept Exception as e:\n    print(\"An error occurred:\", e) \n                 The value returned from  await database.execute_write_fn(...)  will be the return value from your function. \n                 If your function raises an exception that exception will be propagated up to the  await  line. \n                 By default your function will be executed inside a transaction. You can pass  transaction=False  to disable this behavior, though if you do that you should be careful to manually apply transactions - ideally using the  with conn:  pattern, or you may see  OperationalError: database table is locked  errors. \n                 If you specify  block=False  the method becomes fire-and-forget, queueing your function to be executed and then allowing your code after the call to  .execute_write_fn()  to continue running while the underlying thread waits for an opportunity to run your function. A UUID representing the queued task will be returned. Any exceptions in your code will be silently swallowed.", "breadcrumbs": "[\"Internals for plugins\", \"Database class\"]", "references": "[]"}