snippet.py

@transaction.commit_manually
def foo():
    db.execute("SELECT ...")
    bar()
    db.execute("SELECT ...")
    transaction.commit()

def bar():
    db.execute("INSERT ...")

### the above is exactly the same as ....

@transaction.commit_manually
def foo():
    db.execute("SELECT ...")
    db.execute("INSERT ...")    # <--- as if bar was inlined
    db.execute("SELECT ...")
    transaction.commit()

### and remember that decorators aren't "magic", they just run code before a function
### so the above is also the same as ...

                                # <---- no decorator
def foo():
    transaction.managed(True)   # <---- it's a little more complex, but that's basically all commit_manually does!
    db.execute("SELECT ...")
    db.execute("INSERT ...")    # <--- Or a call to bar() here, same thing
    db.execute("SELECT ...")
    transaction.commit()