How to use PyVISA - 10 common examples

raise InvalidBinaryFormat
        if fmt & 0x04 == big_endian:
            endianess = ">"
        else:
            endianess = "<"
        try:
            if fmt & 0x03 == single:
                result = list(struct.unpack((endianess +
                                             str(data_length // 4) + "f").encode('ascii'), data))
            elif fmt & 0x03 == double:
                result = list(struct.unpack(endianess +
                                            str(data_length // 8) + "d", data))
            else:
                raise ValueError("unknown data values fmt requested")
        except struct.error:
            raise InvalidBinaryFormat("binary data itself was malformed")
        return result

def _test_devices_timeouts(self, resource_name):
        inst = self.rm.open_resource(resource_name, timeout=0.1)
        self.assertRaises(VisaIOError, inst.read)

def setUp(self):
        self._test_handler = None
        if self.CHECK_NO_WARNING:
            self._test_handler = th = TestHandler()
            th.setLevel(logging.WARNING)
            logger.addHandler(th)

def test_InvalidBinaryFormat(self):
        self._test_pickle_unpickle(errors.InvalidBinaryFormat())

def test_ieee_integer(self):
        values = list(range(99))
        containers = (list, tuple) #+ ((np.asarray,) if np else ())
        for fmt in 'bBhHiIfd':
            for endi in (True, False):
                for cont in containers:
                    conv = cont(values)
                    msg = 'fmt=%s, endianness=%s, container=%s' % (fmt, endi, cont.__name__)
                    try:
                        block = util.to_ieee_block(conv, fmt, endi)
                        parsed = util.from_ieee_block(block, fmt, endi, cont)
                    except Exception as e:
                        raise Exception(msg + '\n' + repr(e))

                    self.assertEqual(conv, parsed, msg)

:param resources: iterable of resources.
    :param query: query expression.
    """

    if '{' in query:
        query, _ = query.split('{')
        logger.warning('optional part of the query expression not supported. '
                       'See filter2')

    try:
        query = query.replace('?', '.')
        matcher = re.compile(query, re.IGNORECASE)
    except re.error:
        raise errors.VisaIOError(constants.VI_ERROR_INV_EXPR)

    return tuple(res for res in resources if matcher.match(res))

It accepts the optional part of the expression.

    .. warning: This function is experimental and unsafe as it uses eval,
                It also might require to open the resource.

    :param resources: iterable of resources.
    :param query: query expression.
    :param open_resource: function to open the resource.
    """

    if '{' in query:
        try:
            query, optional = query.split('{')
            optional, _ = optional.split('}')
        except ValueError:
            raise errors.VisaIOError(constants.VI_ERROR_INV_EXPR)
    else:
        optional = None

    filtered = filter(resources, query)

    if not optional:
        return filtered

    optional = optional.replace('&&', 'and').replace('||', 'or').replace('!', 'not ')
    optional = optional.replace('VI_', 'res.VI_')

    class AttrGetter():

        def __init__(self, resource_name):
            self.resource_name = resource_name
            self.parsed = parse_resource_name(resource_name)

def _init(self):
        try:
            lib = Library(self.library_path)
        except OSError as exc:
            raise errors.LibraryError.from_exception(exc, self.library_path)

        self.lib = lib

        # Set the argtypes, restype and errcheck for each function
        # of the visa library. Additionally store in `_functions` the
        # name of the functions.
        functions.set_signatures(self.lib, errcheck=self._return_handler)

        logger.debug('Library signatures: %d ok, %d failed',
                     len(getattr(self.lib, '_functions', [])),
                     len(getattr(self.lib, '_functions_failed', [])))

        # Set the library functions as attributes of the object.
        for method_name in getattr(self.lib, '_functions', []):
            setattr(self, method_name, getattr(self.lib, method_name))

Exp|exp     Matches either the preceding or following expression. The or
                    operator | matches the entire expression that precedes or
                    follows it and not just the character that precedes or follows
                    it. For example, VXI|GPIB means (VXI)|(GPIB), not VX(I|G)PIB.

        (exp)       Grouping characters or expressions.


    :param resources: iterable of resources.
    :param query: query expression.
    """

    if '{' in query:
        query, _ = query.split('{')
        logger.warning('optional part of the query expression not supported. '
                       'See filter2')

    try:
        query = query.replace('?', '.')
        matcher = re.compile(query, re.IGNORECASE)
    except re.error:
        raise errors.VisaIOError(constants.VI_ERROR_INV_EXPR)

    return tuple(res for res in resources if matcher.match(res))

def init(self):
        """Singleton class constructor.

        See vpp43.Singleton for details.

        """
        ResourceTemplate.__init__(self)
        # I have "session" as an alias because the specification calls the "vi"
        # handle "session" for the resource manager.
        self.session = self.vi = vpp43.open_default_resource_manager()