At http://pyvisa.sourceforge.net you can find information about the PyVISA package. It realises Python bindings for the VISA library functions, which enables you to control GPIB, USB, and RS232-serial measurement devices via Python.
Today I released version 1.0. If you have v0.9.7 of last september already, you needn't download it because it contains only minor improvements in the documentation. However, since I've received a couple of positive reports about successful use of PyVISA (and no negatives), I finally dare to jump to 1.0 and declare it stable.
F'up to comp.lang.python