Transactions with Python sqlite3

For anyone who'd like to work with the sqlite3 lib regardless of its shortcomings, I found that you can keep some control of transactions if you do these two things:

1. set Connection.isolation_level = None (as per the docs, this means autocommit mode)
2. avoid using executescript at all, because according to the docs it "issues a COMMIT statement first" - ie, trouble. Indeed I found it interferes with any manually set transactions

So then, the following adaptation of your test works for me:

import sqlite3

sql = sqlite3.connect("/tmp/test.db")
sql.isolation_level = None
c = sql.cursor()
c.execute("begin")
try:
    c.execute("update test set i = 1")
    c.execute("fnord")
    c.execute("update test set i = 0")
    c.execute("commit")
except sql.Error:
    print("failed!")
    c.execute("rollback")

Per the docs,

Connection objects can be used as context managers that automatically commit or rollback transactions. In the event of an exception, the transaction is rolled back; otherwise, the transaction is committed:

Therefore, if you let Python exit the with-statement when an exception occurs, the transaction will be rolled back.

import sqlite3

filename = '/tmp/test.db'
with sqlite3.connect(filename) as conn:
    cursor = conn.cursor()
    sqls = [
        'DROP TABLE IF EXISTS test',
        'CREATE TABLE test (i integer)',
        'INSERT INTO "test" VALUES(99)',]
    for sql in sqls:
        cursor.execute(sql)
try:
    with sqlite3.connect(filename) as conn:
        cursor = conn.cursor()
        sqls = [
            'update test set i = 1',
            'fnord',   # <-- trigger error
            'update test set i = 0',]
        for sql in sqls:
            cursor.execute(sql)
except sqlite3.OperationalError as err:
    print(err)
    # near "fnord": syntax error
with sqlite3.connect(filename) as conn:
    cursor = conn.cursor()
    cursor.execute('SELECT * FROM test')
    for row in cursor:
        print(row)
        # (99,)

yields

(99,)

as expected.