title: Connect as sys user using cx_Oracle in python to local database
body: <p>Trying to connect to Oracle database using Python cx_Oracle. In sqlplus I do use "sqlplus / as sysdba" as I connect to local database.
  I'm trying to use the same method without password in Python, but getting ORA-01017 or ORA-12541</p>
  
  <pre><code>tns_entry=cx_Oracle.makedsn('localhost',1521,'db1')
  
  &gt;&gt;&gt; conn = cx_Oracle.connect(mode = cx_Oracle.SYSDBA,dsn=tns_entry)
  
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  cx_Oracle.DatabaseError: ORA-12541: TNS:no listener
  
  &gt;&gt;&gt; conn = cx_Oracle.connect("/",mode = cx_Oracle.SYSDBA,dsn=tns_entry)
  
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  cx_Oracle.DatabaseError: ORA-12541: TNS:no listener
  &gt;&gt;&gt; conn = cx_Oracle.connect(mode = cx_Oracle.SYSDBA,dsn="TNS SERVICE")
  
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  cx_Oracle.DatabaseError: ORA-01017: invalid username/password; logon denied
  </code></pre>
  
  <p>Where am I going wrong? Please provide your input. Thanks</p>