I wholeheartedly agree with KM. Just for the sake of completeness, I will mention some arguments against using non-standard modules:

• Learning how to do something yourself may be a worthwhile learning experience.
• The module that does what you need may include a lot of extra functionality that you are not going to use. In those cases, sometimes it's good to peek under the hood and only extract the functionality you need (giving proper credit, and ideally asking for permission from the author) and putting it directly in your program

Of course, this only applies to modules that do relatively simple things. If you need to do database access or write a CGI script. By all means, please, use the modules. There's no need to reinvent the wheel, particularly when it's a complex wheel.

--ZZamboni