title: Update a PostgreSQL array using SQLAlchemy
body: <p>I'm trying to update an integer array on a PostgreSQL table using a SQL statement in SQLAlchemy Core. I first tried using the query generator, but couldn't figure out how to do that either. I believe that Psycopg2, which is the dialect that I'm using, can automatically form the array into a format that PostgreSQL can accept.</p>
  
  <p>Here's the table schema:</p>
  
  <pre><code>CREATE TABLE surveys (
      survey_id serial PRIMARY KEY,
      question_ids_ordered INTEGER[],
      created_at TIMESTAMP NOT NULL DEFAULT now(),
  );
  </code></pre>
  
  <p>And the SQLAlchemy statement:</p>
  
  <pre><code>survey_id = 46
  question_ids_ordered = [237, 238, 239, 240, 241, 242, 243]
  
  with engine.begin() as conn:
      conn.execute("""UPDATE surveys
                      SET question_ids_ordered = %s
                      WHERE survey_id = %s""",
                      question_ids_ordered, survey_id)
  </code></pre>
  
  <p>And the traceback I receive is:</p>
  
  <pre><code>Traceback (most recent call last):
    File "foo.py", line 16, in &lt;module&gt;
      res = add_question_to_group(current_user, 46, 358, question_ids_ordered, new_group_name="Jellyfish?")
    File "/vagrant/workspace/panel/panel/survey.py", line 80, in add_question_to_group
      question_ids_ordered, survey_id)
    File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 664, in execute
      params)
    File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 808, in _execute_text
      statement, parameters
    File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 831, in _execute_context
      None, None)
    File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 827, in _execute_context
      context = constructor(dialect, self, conn, *args)
    File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/default.py", line 513, in _init_statement
      for p in parameters]
  sqlalchemy.exc.StatementError: 'int' object is not iterable (original cause: TypeError: 'int' object is not iterable) 'UPDATE surveys\n                        SET question_ids_ordered = %s\n                        WHERE survey_id = %s' ([237, 238, 239, 240, 241, 242, 243], 46)
  </code></pre>
  
  <p>What am I doing wrong?</p>