On Monday 23 May 2011, eigenroot elucidated thus: > Hello everyone, > > I would like to control a Keithley source meter with PyVISA in the > lab. The operating system is Scientific Linux 5.5, and the Python > version is 2.4. I first installed NI-VISA's Linux package ( > http://joule.ni.com/nidu/cds/view/p/id/2040/lang/en) which was > compatible with Scientific Linux 5, and then ctypes from > http://python.net/crew/theller/ctypes/ and linux-gpib from > http://linux-gpib.sourceforge.net/. After everything was done > successfully I fired up an interactive Python session, and typed > > import visa > > No errors. And then I typed > > keithley = visa.instrument("GPIB::25") > > but got errors: > > Traceback (most recent call last): > File "<stdin>", line 1, in ? > File "/usr/lib/python2.4/site-packages/pyvisa/visa.py", line 287, > in instrument > interface_type, _ = \ > File "/usr/lib/python2.4/site-packages/pyvisa/vpp43.py", line 777, > in parse_resource > byref(interface_board_number)) > File "/usr/lib/python2.4/site-packages/pyvisa/vpp43.py", line 398, > in check_status > raise visa_exceptions.VisaIOError, status > pyvisa.visa_exceptions.VisaIOError: VI_ERROR_LIBRARY_NFOUND: A code > library required by VISA could not be located or loaded. > > > Could anyone please help? Thanks very much~! Is the library installed? Where is it installed? I've discovered that ctypes isn't always that smart. It might be looking for it in /usr/lib, but the library you want might be in /usr/local/lib, in which case, it might not be found. j -- Joshua J. Kugler - Fairbanks, Alaska Azariah Enterprises - Programming and Website Design [log in to unmask] - Jabber: [log in to unmask] PGP Key: http://pgp.mit.edu/ ID 0x73B13B6A