How do you change the SQL isolation level from Python using MySQLdb?

I don't think this works for the MySQLdb driver; you'll have to issue separate queries:

cur = conn.cursor()
cur.execute("SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED")
cur.execute("SELECT @@session.tx_isolation")
print cur.fetchall()[0]
cur.execute("SELECT * FROM bar")
print cur.fetchall()
cur.execute("SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ")
cur.execute("SELECT @@session.tx_isolation")
print cur.fetchall()[0]

# output
('READ-UNCOMMITTED',)
(('foo',), ('bar',))
('REPEATABLE-READ',)

The MySQLdb cursor's execute() method only sees the first query up to the semicolon:

cur.execute("SELECT * FROM bar WHERE thing = 'bar'; SELECT * FROM bar")
print cur.fetchall()

# output
(('bar',),)