import sqlite3

key = '1234567789'
conn = sqlite3.connect('/tmp/sqlite.db', isolation_level=None, check_same_thread=False)
conn.execute('PRAGMA journal_mode = OFF')
MAKE_TABLE = 'CREATE TABLE IF NOT EXISTS t (key TEXT PRIMARY KEY)'
conn.execute(MAKE_TABLE)
conn.commit()

cur = conn.cursor()
for i in range(1, 50000):
    HAS_ITEM = 'SELECT 1 FROM t WHERE key = ?'
    conn.execute(HAS_ITEM, (key,))
    selected = cur.fetchone()
    if selected is None:
        ADD_ITEM = 'REPLACE INTO t (key) VALUES (?)'
        conn.execute(ADD_ITEM, (key,))