title: Can't connect the postgreSQL with psycopg2
body: <p>It's the first time that I can't find the answer about some tech problems
  Here's my problems:</p>
  
  <pre><code>&gt;&gt; conn=psycopg2.connect(database="mydb", user="postgres", password="123",port=5432)
  
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  psycopg2.OperationalError: could not connect to server: No such file or directory
      Is the server running locally and accepting
      connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
  </code></pre>
  
  <ol>
  <li>My postgreSQL is running</li>
  <li>My listeningport is 5432 for sure</li>
  <li>root@lanston-laptop:~# psql -l
  Password: </li>
  </ol>
  
  <pre>
                                         List of databases
           Name      |  Owner   | Encoding | Collation  |   Ctype    |   Access privileges 
      ---------------+----------+----------+------------+------------+-----------------------
       checkdatabase | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
       mydb          | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
       postgres      | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
       template0     | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
                     |          |          |            |            | postgres=CTc/postgres
       template1     | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
                     |          |          |            |            | postgres=CTc/postgres
  </pre>
  
  <p>Thanks a lot!</p>