Lesson 11 — Transactions

Transactions with "with db:"

A transaction makes several changes atomic: all succeed or none do. Python's sqlite3 gives a clean way: with db: commits when the block ends normally and rolls back (undoes) everything if an error escapes the block.

with db:
    db.execute("INSERT ...")
    db.execute("INSERT ...")   # if this fails, the first is undone too

Why it matters: an order without its order lines, or stock reduced without a sale, is corrupt data. Transactions prevent half-finished work.