Python packages for CSV, EXCEL, Oracle DB, Greenplum, PostgresSQL, Cfg File

1) Python csv module gives directly support for CSV
Reference Link:
http://docs.python.org/library/csv.html

2) For excel manipulation, there are two well-known packages:
xlrd/xlwd/xlutils, which are pure Python, can work on any platform
Reference Link:
http://www.python-excel.org/

win32com.client, a.k.a Python Windows extension,  which is com based, and only works on Windows
Reference Link:
http://starship.python.net/crew/mhammond/win32/Downloads.html

3)  For Oracle DB,  cx_Oracle is the most well-known
Reference Link:
http://cx-oracle.sourceforge.net/html/index.html#
http://st-curriculum.oracle.com/obe/db/11g/r2/prod/appdev/opensrclang/python/python.htm

4) For Greenplum/PostgreSQL, there are two well-known pacages:
psycopg2
Reference Link:
http://www.initd.org/psycopg/download/

PyGreSQL
Reference Link:
http://www.pygresql.org/

5) Python ConfigureParser module provide direct supports for cfg-like file manipulation
Reference Link:
http://docs.python.org/library/configparser.html#module-ConfigParser

How to pick among them ?
Google please and read the their docs.