I need to convert the GPIB to USB using NI-488.2 from national instrument and I need to create a software complete with GUI using python. The old machine that my company use for measuring is Model 273A potentiostat/galvanostat from Princeton Applied Research. Im using windows 7 and python 2.7 using wxpython. And I need to program using python. I just need to send simple command for example R to run the machine.
Connections : from measuring machine via GPIB to NI-488.2(a card to convert GPIB to usb)
              from NI-488.2 to pc via usb
The questions are :

How can I send any command to the machine? From what I know, I need to send it to the driver of the NI-488.2. Is it correct? (if correct see ques. 2 if not jump to ques. 3)
How can I send from my own code using python to the NI-488.2 driver?
How to see the code of any driver? But in my case the driver for NI-488.2. (the driver can be downloaded for free in the national instrument website but registration needed)
You need to install the driver for the GPIB-USB cable, and registration process is quite simple. For the registration, basically you just need to leave a email address of yours. 
After you install the driver, you can find many useful information in their "help". Generally you need to read the user manual of your device. The idea is that you should use ctypes to interface with the GPIB-USB's dll in Python.
converting GPIB to USB using NI-488.2