Method begin

lib/sqlalchemy/engine/base.py:808–881

Begin a transaction prior to autobegin occurring. E.g.:: with engine.connect() as conn: with conn.begin() as trans: conn.execute(table.insert(), {"username": "sandy"}) The returned object is an instance of :class:`_engine.RootTransac

(self)

            self.begin()

    def begin(self) -> RootTransaction:
        """Begin a transaction prior to autobegin occurring.

        E.g.::

            with engine.connect() as conn:
                with conn.begin() as trans:
                    conn.execute(table.insert(), {"username": "sandy"})

        The returned object is an instance of :class:`_engine.RootTransaction`.
        This object represents the "scope" of the transaction,
        which completes when either the :meth:`_engine.Transaction.rollback`
        or :meth:`_engine.Transaction.commit` method is called; the object
        also works as a context manager as illustrated above.

        The :meth:`_engine.Connection.begin` method begins a
        transaction that normally will be begun in any case when the connection
        is first used to execute a statement.  The reason this method might be
        used would be to invoke the :meth:`_events.ConnectionEvents.begin`
        event at a specific time, or to organize code within the scope of a
        connection checkout in terms of context managed blocks, such as::

            with engine.connect() as conn:
                with conn.begin():
                    conn.execute(...)
                    conn.execute(...)

                with conn.begin():
                    conn.execute(...)
                    conn.execute(...)

        The above code is not  fundamentally any different in its behavior than
        the following code  which does not use
        :meth:`_engine.Connection.begin`; the below style is known
        as "commit as you go" style::

            with engine.connect() as conn:
                conn.execute(...)
                conn.execute(...)
                conn.commit()

                conn.execute(...)
                conn.execute(...)
                conn.commit()

        From a database point of view, the :meth:`_engine.Connection.begin`
        method does not emit any SQL or change the state of the underlying
        DBAPI connection in any way; the Python DBAPI does not have any
        concept of explicit transaction begin.

        .. seealso::

            :ref:`tutorial_working_with_transactions` - in the
            :ref:`unified_tutorial`

            :meth:`_engine.Connection.begin_nested` - use a SAVEPOINT

            :meth:`_engine.Connection.begin_twophase` -