title: Connecting postgresql with sqlalchemy
body: <p>I know this might be really a simple question but I don't know the solution. What is happening here when I try to connect to postgresql? I am self learner in this field of database and programming so please be gentle with me.
  When I try following code:</p>
  
  <pre><code>import sqlalchemy
  db = sqlalchemy.create_engine('postgresql:///tutorial.db')
  </code></pre>
  
  <p>I get this error:</p>
  
  <blockquote>
    <p>Traceback (most recent call last):
       File "", line 1, in 
        db = sqlalchemy.create_engine('postgresql:///tutorial.db')
      File "C:\Python27\lib\site-packages\sqlalchemy-0.7.5dev-py2.7.egg\sqlalchemy\engine__init__.py", line 327, in create_engine
        return strategy.create(*args, **kwargs)
      File "C:\Python27\lib\site-packages\sqlalchemy-0.7.5dev-py2.7.egg\sqlalchemy\engine\strategies.py", line 64, in create
        dbapi = dialect_cls.dbapi(**dbapi_args)
      File "C:\Python27\lib\site-packages\sqlalchemy-0.7.5dev-py2.7.egg\sqlalchemy\dialects\postgresql\psycopg2.py", line 289, in dbapi
        psycopg = <strong>import</strong>('psycopg2')
    ImportError: No module named psycopg2</p>
  </blockquote>
  
  <p>Do I need to install psycopg2 separately? What is the correct connection string for postgresql?</p>