PsychoPy can access a wide range of external hardware. For some devices the interface has already been created in the following sub-packages of PsychoPy. For others you may need to write the code to access the serial port etc. manually.
Try to find a connected photometer/photospectrometer! PsychoPy will sweep a series of serial ports trying to open them. If a port successfully opens then it will try to issue a command to the device. If it responds with one of the expected values then it is assumed to be the appropriate device.
photom = findPhotometer(device='PR655') #sweeps ports 0 to 10 searching for a PR655 print photom.getLum() if hasattr(photom, 'getSpectrum'):#can retrieve spectrum (e.g. a PR650) print photom.getSpectrum()