title: SQL Alchemy update table using list of dicts with bindparam not working
body: <p>I'm trying to perform an update based on a list of dictionaries using bindparam, but I'm not sure why this example isn't working:</p>
  
  <pre><code>import sqlalchemy
  from sqlalchemy import Table, exc, and_
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy.sql.expression import bindparam
  from sqlalchemy.orm import sessionmaker
  
  con_string = 'mysql+mysqlconnector://{login}:{passwd}@{hostname}:{port}/{db}'
  
  engine_str = con_string.format(
      login=login, passwd=pwd, hostname=hostname, port=db_port, db=db_name
  )
  
  try:
      engine = sqlalchemy.create_engine(engine_str, echo=False)
      session = sessionmaker(bind=engine)
      connection = engine.connect()
      session = session(bind=connection)
      Base = declarative_base()
  except exc.SQLAlchemyError:
      raise
  
  
  
  def bulk_updater(data):
      for i in data:
          print i
      t = Table('demo_table', Base.metadata, autoload_with=engine)
      try:
          stm = t.update().where(
              t.c.trigger_service == bindparam('trigger_service')).values={package_name: 'package_name'}
          connection.execute(stm, data)
      finally:
          session.close()
  
  d = [{'package_name': 'something', 'trigger_service': 'somewhere'}, {'package_name': 'somesome', 'trigger_service': 'wherewhere'}]
  bulk_updateer(d)
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>It seems the problem is when using bindparam here, because when i force the value it works perfectly. Still trying to understand why isn't working.</p>
  
  <pre><code>t.c.trigger_service == bindparam('trigger_service')
  </code></pre>