I'm working for small company, which operates in the automation industry.
The boss hired me because he wants to sell/give some desktop applications to his
current costumers.
He imposes me to use the Netbeans Platform (a generic desktop application framework).
A software engineer friend of his advised him to choose this framework. 
At the moment I created 3 desktop applications with Netbeans Platform.
I like Netbeans Platfom. I really take advantage of modularity, Window System and Lookup.
Unfortunately I'm frustrated to known that I can do the same works with Python and PyQt in a fraction of time.
I've already illustrated to my boss the main advantages of Python, but he doesn't like the
idea to use a language that he never heared of it.
I'm the only programmer who codes desktop applications. And except the framework imposition, I'm free to use whatever I want.
I'm looking for good motivations to convince him to leave Netbeans Platform for Python/PyQt.
P.S: My english is bad, sorry.
The problem is that development time is usually nothing compared to maintenance.  Who cares if it takes two days instead of four if the app has a 1-5 year lifetime?
You'll have to convince him that if you get hit by a truck or leave the company (perhaps to work for somebody who uses Python exclusively) that he won't be left in the lurch with a bunch of applications that nobody else knows and can't maintain or upgrade.
How to convince boss to substitute Java/Netbeans Platform for Python/PyQt?