sqlite3.OperationalError: Database is Locked

Why This Happens

SQLite uses file-level locking for writes. When one connection is writing, all others are blocked. Long transactions and unclosed connections cause this.

The Problem

import sqlite3
conn1 = sqlite3.connect('app.db')
conn1.execute('BEGIN EXCLUSIVE')
conn2 = sqlite3.connect('app.db')
conn2.execute('INSERT INTO t VALUES (1)')

The Fix

import sqlite3
conn = sqlite3.connect('app.db', timeout=10)
conn.execute('PRAGMA journal_mode=WAL')

with sqlite3.connect('app.db') as conn:
    conn.execute('INSERT INTO t VALUES (?)', (1,))

Step-by-Step Fix

1. 1

   Enable WAL mode

   Run PRAGMA journal_mode=WAL for better concurrency.

2. 2

   Use context managers

   Use 'with conn:' for prompt commits.

3. 3

   Set a timeout

   Use timeout=10 to wait for locks instead of failing.