Hi Mark, many thanks for your hints.
> --------------- func.py ------------------ > import ctypes as c > > # int func (int numVars, char **varNames, int *varTypes) > > INT = c.c_int > PINT = c.POINTER(INT) > PCHAR = c.c_char_p > PPCHAR = c.POINTER(PCHAR) > > func = c.CDLL('func').func > func.restype = None > func.argtypes = [INT,PPCHAR,PINT] > > numVars = 3 > varNames = (PCHAR * numVars)('abc','def','ghi') > varTypes = (INT * numVars)(1,2,3) > > func(numVars,varNames,varTypes) The function to call has the following signiture: int SetVarLabel(int handle, const char *varName, const char *varLabel) I did as you suggested by doing the following: INT = c_int PCHAR = c_char_p libc.argtypes = [INT,PCHAR,PCHAR] vn = create_string_buffer("var1") vl = create_string_buffer("Label") print "vn: ", vn.value print "vl: ", vl.value returnCode = libc.SetVarLabel(h,byref(vn), byref(vl)) print "Return Code: ", returnCode The return code is always "variable not found". Thus my call to the C library is not working. What do I do wrong? Best regards Georg -- http://mail.python.org/mailman/listinfo/python-list