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A quick tour (original)

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Quick tour

This quick tour will guide you through the first steps on using PyTango. This is the new quick tour guide based on the ITango console. You can still find the old version of this tour based on a simple python console here.

Quick tour on the client side

Check PyTango version

Start an IPython tango console with:

$ itango

and type:

ITango [1]: PyTango.__version__
Result [1]: '8.0.0'

ITango [2]: PyTango.__version_long__
Result [2]: '8.0.0dev0'

ITango [3]: PyTango.__version_number__
Result [3]: 800

ITango [4]: PyTango.__version_description__
Result [4]: 'This version implements the C++ Tango 8.0 API.'

or alternatively:

ITango [1]: PyTango.Release.version
Result [1]: '8.0.0'

ITango [2]: PyTango.Release.version_long
Result [2]: '8.0.0dev0'

ITango [3]: PyTango.Release.version_number
Result [3]: 800

ITango [4]: PyTango.Release.version_description
Result [4]: 'This version implements the C++ Tango 8.0 API.'

Tip

When typing, try pressing <tab>. Since ITango has autocomplete embedded you should get a list of possible completions. Example:

PyTango.Release.<tab>

Should get a list of all members of PyTango.Release class.

Check Tango C++ version

From a client (This is only possible since PyTango 7.0.0)

ITango [1]: import PyTango.constants

ITango [2]: PyTango.constants.TgLibVers
Result [2]: '8.0.0'

From a server you can alternatively do:

u = PyTango.Util.instance()
tg_cpp_lib_ver = u.get_tango_lib_release()

Test the connection to the Device and get it’s current state

One of the most basic examples is to get a reference to a device and determine if it is running or not.

ITango [1]: # What is a DeviceProxy, really?
ITango [1]: DeviceProxy?
DeviceProxy is the high level Tango object which provides the client with
an easy-to-use interface to TANGO devices. DeviceProxy provides interfaces
to all TANGO Device interfaces.The DeviceProxy manages timeouts, stateless
connections and reconnection if the device server is restarted. To create
a DeviceProxy, a Tango Device name must be set in the object constructor.

Example :
   dev = PyTango.DeviceProxy("sys/tg_test/1")

ITango [2]: tangotest = DeviceProxy("sys/tg_test/1")

ITango [3]: # ping it
ITango [4]: tangotest.ping()
Result [4]: 110

ITango [5]: # Lets test the state
ITango [6]: tangotest.state()
Result [6]: PyTango._PyTango.DevState.RUNNING

ITango [7]: # And now the status
ITango [8]: tangotest.status()
Result [8]: 'The device is in RUNNING state.'

Note

Did you notice that you didn’t write PyTango.DeviceProxy but instead just DeviceProxy ? This is because ITango automatically exports the DeviceProxy, AttributeProxy, Database and Group classes to the namespace. If you are writting code outside ITango you MUST use the PyTango module prefix.

Tip

When typing the device name in the DeviceProxy creation line, try pressing the <tab> key. You should get a list of devices:

tangotest = DeviceProxy("sys<tab>

Better yet (and since the Tango Class of ‘sys/tg_test/1’ is ‘TangoTest’), try doing:

tangotest = TangoTest("<tab>

Now the list of devices should be reduced to the ones that belong to the ‘TangoTest’ class. Note that TangoTest only works in ITango. If you are writting code outside ITango you MUST use PyTango.DeviceProxy instead.

Execute commands with scalar arguments on a Device

As you can see in the following example, when scalar types are used, PyTango automatically manages the data types, and writing scripts is quite easy.

ITango [1]: tangotest = TangoTest("sys/tg_test/1")

ITango [2]: # classical way
ITango [2]: r = tangotest.command_inout("DevString", "Hello, world!")

ITango [3]: print "Result of execution of DevString command =", r
Result of execution of DevString command = Hello, world!

ITango [4]: # 'pythonic' way
ITango [5]: tangotest.DevString("Hello, world!")
Result [5]: 'Hello, world!'

ITango [6]: # type is automatically managed by PyTango
ITango [7]: tangotest.DevULong(12456)
Result [7]: 12456

Execute commands with more complex types

In this case you have to use put your arguments data in the correct python structures.

ITango [1]: tangotest = TangoTest("sys/tg_test/1")

ITango [2]: argin = [1, 2, 3], ["Hello", "World"]

ITango [3]: tango_test.DevVarLongArray(argin)
Result [3]: [array([1, 2, 3]), ['Hello', 'World']]

Note

notice that the command returns a list of two elements. The first element is a numpy.ndarray (assuming PyTango is compiled with numpy support). This is because PyTango does a best effort to convert all numeric array types to numpy arrays.

Reading and writing attributes

Basic read/write attribute operations.

ITango [1]: # Read a scalar attribute
ITango [2]: print tangotest.read_attribute("long_scalar")
DeviceAttribute[
data_format = PyTango._PyTango.AttrDataFormat.SCALAR
      dim_x = 1
      dim_y = 0
 has_failed = False
   is_empty = False
       name = 'long_scalar'
    nb_read = 1
 nb_written = 1
    quality = PyTango._PyTango.AttrQuality.ATTR_VALID
r_dimension = AttributeDimension(dim_x = 1, dim_y = 0)
       time = TimeVal(tv_nsec = 0, tv_sec = 1281084943, tv_usec = 461730)
       type = PyTango._PyTango.CmdArgType.DevLong
      value = 239
    w_dim_x = 1
    w_dim_y = 0
w_dimension = AttributeDimension(dim_x = 1, dim_y = 0)
    w_value = 0]

ITango [3]: # Read a spectrum attribute
ITango [4]: print tangotest.read_attribute("double_spectrum")
DeviceAttribute[
data_format = PyTango._PyTango.AttrDataFormat.SPECTRUM
      dim_x = 20
      dim_y = 0
 has_failed = False
   is_empty = False
       name = 'double_spectrum'
    nb_read = 20
 nb_written = 20
    quality = PyTango._PyTango.AttrQuality.ATTR_VALID
r_dimension = AttributeDimension(dim_x = 20, dim_y = 0)
       time = TimeVal(tv_nsec = 0, tv_sec = 1281085195, tv_usec = 244760)
       type = PyTango._PyTango.CmdArgType.DevDouble
      value = array([  0.,   1.,   2.,   3.,   4.,   5.,   6.,   7.,   8.,   9.,  10.,
        11.,  12.,  13.,  14.,  15.,  16.,  17.,  18.,  19.])
    w_dim_x = 20
    w_dim_y = 0
w_dimension = AttributeDimension(dim_x = 20, dim_y = 0)
    w_value = array([  0.,   1.,   2.,   3.,   4.,   5.,   6.,   7.,   8.,   9.,  10.,
        11.,  12.,  13.,  14.,  15.,  16.,  17.,  18.,  19.])]

ITango [5]: # Write a scalar attribute
ITango [6]: scalar_value = 18
ITango [7]: tangotest.write_attribute("long_scalar", scalar_value)

ITango [8]: # Write a spectrum attribute
ITango [9]: spectrum_value = numpy.random.rand(100)*10
ITango [10]: tangotest.write_attribute("double_spectrum", spectrum_value)


ITango [11]: # Write an image attribute
ITango [12]: image_value = numpy.random.randint(0,10,size=(10,10))
ITango [13]: tangotest.write_attribute("long_image", image_value)

Tip

If you are only interested in the attribute’s read value you can do insted:

ITango [1]: tangotest.long_scalar
Result [1]: 239

The same is valid for writting a new value to an attribute:

ITango [1]: tangotest.long_scalar = 18

Note

If PyTango is compiled with numpy support the values got when reading a spectrum or an image will be numpy arrays. This results in a faster and more memory efficient PyTango. You can also use numpy to specify the values when writing attributes, especially if you know the exact attribute type.:

# Creating an unitialized double spectrum of 1000 elements
spectrum_value = PyTango.numpy_spectrum(PyTango.DevDouble, 1000)

# Creating an spectrum with a range
# Note that I do NOT use PyTango.DevLong here, BUT PyTango.NumpyType.DevLong
# numpy functions do not understand normal python types, so there's a
# translation available in PyTango.NumpyType
spectrum_value = numpy.arange(5, 1000, 2, PyTango.NumpyType.DevLong)

# Creating a 2x2 long image from an existing one
image_value = PyTango.numpy_image(PyTango.DevLong, [[1,2],[3,4]])

Registering devices

Defining devices in the Tango DataBase:

ITango [1]: # The 3 devices name we want to create
ITango [2]: # Note: these 3 devices will be served by the same DServer
ITango [3]: new_device_name1="px1/tdl/mouse1"
ITango [4]: new_device_name2="px1/tdl/mouse2"
ITango [5]: new_device_name3="px1/tdl/mouse3"

ITango [6]: # Define the Tango Class served by this DServer
ITango [7]: new_device_info_mouse = PyTango.DbDevInfo()
ITango [8]: new_device_info_mouse._class = "Mouse"
ITango [9]: new_device_info_mouse.server = "ds_Mouse/server_mouse"

ITango [10]: # add the first device
ITango [11]: new_device_info_mouse.name = new_device_name1
ITango [12]: db.add_device(new_device_info_mouse)

ITango [13]: # add the next device
ITango [14]: new_device_info_mouse.name = new_device_name2
ITango [15]: db.add_device(new_device_info_mouse)

ITango [16]: # add the third device
ITango [17]: new_device_info_mouse.name = new_device_name3
ITango [18]: db.add_device(new_device_info_mouse)

Setting up Device properties

A more complex example using python subtilities. The following python script example (containing some functions and instructions manipulating a Galil motor axis device server) gives an idea of how the Tango API should be accessed from Python.

ITango [1]: # connecting to the motor axis device
ITango [2]: axis1 = DeviceProxy ("microxas/motorisation/galilbox")

ITango [3]: # Getting Device Properties
ITango [4]: property_names = ["AxisBoxAttachement",
      ....:                   "AxisEncoderType",
      ....:                   "AxisNumber",
      ....:                   "CurrentAcceleration",
      ....:                   "CurrentAccuracy",
      ....:                   "CurrentBacklash",
      ....:                   "CurrentDeceleration",
      ....:                   "CurrentDirection",
      ....:                   "CurrentMotionAccuracy",
      ....:                   "CurrentOvershoot",
      ....:                   "CurrentRetry",
      ....:                   "CurrentScale",
      ....:                   "CurrentSpeed",
      ....:                   "CurrentVelocity",
      ....:                   "EncoderMotorRatio",
      ....:                   "logging_level",
      ....:                   "logging_target",
      ....:                   "UserEncoderRatio",
      ....:                   "UserOffset"]

ITango [5]: axis_properties = axis1.get_property(property_names)
ITango [6]: for prop in axis_properties.keys():
      ....:     print "%s: %s" % (prop, axis_properties[prop][0])

ITango [7]: # Changing Properties
ITango [8]: axis_properties["AxisBoxAttachement"] = ["microxas/motorisation/galilbox"]
ITango [9]: axis_properties["AxisEncoderType"] = ["1"]
ITango [10]: axis_properties["AxisNumber"] = ["6"]
ITango [11]: axis1.put_property(axis_properties)

ITango [12]: # Reading attributes
ITango [13]: att_list = axis.get_attribute_list()
ITango [14]: for att in att_list:
       ....:     att_val = axis.read_attribute(att)
       ....:     print "%s: %s" % (att.name, att_val.value)

ITango [15]: # Changing some attribute values
ITango [16]: axis1.write_attribute("AxisBackslash", 0.5)
ITango [17]: axis1.write_attribute("AxisDirection", 1.0)
ITango [18]: axis1.write_attribute("AxisVelocity", 1000.0)
ITango [19]: axis1.write_attribute("AxisOvershoot", 500.0)

ITango [20]: # Testing some device commands
ITango [21]: pos1=axis1.read_attribute("AxisCurrentPosition")
ITango [22]: axis1.command_inout("AxisBackward")
ITango [23]: while pos1.value > 1000.0:
       ....:     pos1 = axis1.read_attribute("AxisCurrentPosition")
       ....:     print "position axis 1 = ", pos1.value

ITango [24]: axis1.command_inout("AxisStop")

Quick tour on the server side

To write a tango device server in python, you must first import the PyTango module in your code.

Below is the python code for a Tango device server with two commands and two attributes. The commands are:

  1. IOLOng which receives a Tango Long and return it multiply by 2. This command is allowed only if the device is in the ON state.
  2. IOStringArray which receives an array of Tango strings and which returns it but in the reverse order. This command is only allowed if the device is in the ON state.

The attributes are:

  1. Long_attr wich is a Tango long attribute, Scalar and Read only with a minimum alarm set to 1000 and a maximum alarm set to 1500
  2. Short_attr_rw which is a Tango short attribute, Scalar and Read/Write

The following code is the complete device server code:

import PyTango

class PyDsExp(PyTango.Device_4Impl):

    def __init__(self,cl,name):
        PyTango.Device_4Impl.__init__(self,cl,name)
        self.debug_stream('In PyDsExp __init__')
        PyDsExp.init_device(self)

    def init_device(self):
        self.debug_stream('In Python init_device method')
        self.set_state(PyTango.DevState.ON)
        self.attr_short_rw = 66
        self.attr_long = 1246

    def delete_device(self):
        self.debug_stream('[delete_device] for device %s ' % self.get_name())

    #------------------------------------------------------------------
    # COMMANDS
    #------------------------------------------------------------------

    def is_IOLong_allowed(self):
        return self.get_state() == PyTango.DevState.ON

    def IOLong(self, in_data):
        self.debug_stream('[IOLong::execute] received number %s' % str(in_data))
        in_data = in_data * 2;
        self.debug_stream('[IOLong::execute] return number %s' % str(in_data))
        return in_data;

    def is_IOStringArray_allowed(self):
        return self.get_state() == PyTango.DevState.ON

    def IOStringArray(self, in_data):
        l = range(len(in_data)-1, -1, -1);
        out_index=0
        out_data=[]
        for i in l:
            self.debug_stream('[IOStringArray::execute] received String' % in_data[out_index])
            out_data.append(in_data[i])
            self.debug_stream('[IOStringArray::execute] return String %s' %out_data[out_index])
            out_index += 1
        self.y = out_data
        return out_data

    #------------------------------------------------------------------
    # ATTRIBUTES
    #------------------------------------------------------------------

    def read_attr_hardware(self, data):
        self.debug_stream('In read_attr_hardware')

    def read_Long_attr(self, the_att):
        self.debug_stream('[PyDsExp::read_attr] attribute name Long_attr')
        the_att.set_value(self.attr_long)

    def read_Short_attr_rw(self, the_att):
        self.debug_stream('[PyDsExp::read_attr] attribute name Short_attr_rw')
        the_att.set_value(self.attr_short_rw)

    def write_Short_attr_rw(self, the_att):
        self.debug_stream('In write_Short_attr_rw for attribute %s' % the_att.get_name())
        data = the_att.get_write_value()
        self.attr_short_rw = data[0]


class PyDsExpClass(PyTango.DeviceClass):

    def __init__(self, name):
        PyTango.DeviceClass.__init__(self, name)
        self.set_type("PyDsExp")

    cmd_list = { 'IOLong' : [ [ PyTango.ArgType.DevLong, "Number" ],
                              [ PyTango.ArgType.DevLong, "Number * 2" ] ],
                 'IOStringArray' : [ [ PyTango.ArgType.DevVarStringArray, "Array of string" ],
                                     [ PyTango.ArgType.DevVarStringArray, "This reversed array"] ],
    }

    attr_list = { 'Long_attr' : [ [ PyTango.ArgType.DevLong ,
                                    PyTango.AttrDataFormat.SCALAR ,
                                    PyTango.AttrWriteType.READ],
                                  { 'min alarm' : 1000, 'max alarm' : 1500 } ],

                 'Short_attr_rw' : [ [ PyTango.ArgType.DevShort,
                                       PyTango.AttrDataFormat.SCALAR,
                                       PyTango.AttrWriteType.READ_WRITE ] ]
    }


def main():
    PyTango.server_run({"PyDsExp" : (PyDsExpClass, PyDsExp)})

if __name__ == '__main__':
    main()