My list of short recipes for common tasks ... please check official documentation first! 


Before anything else

import PyTango

Installation notes 

The new PyTango, release 7.1.3 (source only), is now available to download from the Tango download page:

or PiPy:

If you have already installed PyTango 7.x.x with easy_install you can simply update your PyTango version to 7.1.3 by doing:

% easy_install -U PyTango

The documentation is available at:

If you encounter problems installing or running this release, please report them back to the tango mailing list.

This version has been tagged Release_7_1_3

You can check out this version:

svn co PyTango-7.1.3

You can check out the latest version:

svn co PyTango-latest

Nice PyTango dancing

Tiago Coutinho

Using the DeviceProxy object

Getting the polling buffer values

Only for polled attributes we can get the last N read values. the polling buffer depth is managed by the admin device.

dp = PyTango.DeviceProxy('some/tango/device')

Get/Set polled attributes

def get_polled_attributes(dev_name):
    dp = PyTango.DeviceProxy(dev_name)
    attrs = dp.get_attribute_list()
    periods = [(a,dp.get_attribute_poll_period(a)) for a in attrs]
    return dict((a,p) for a,p in periods if p)

[plc4.poll_attribute(a,5000) for k,v in periods if v]

Modify the polling of attributes

import re,PyTango
period = 10000
devs = PyTango.Database().get_device_exported('some/tango/devices*')
for dev in devs:
  dp = PyTango.DeviceProxy(dev)
  attrs = sorted([a for a in dp.get_attribute_list() if re.match('(Output|Temperature)_[0-9]$',a)])
  [dp.poll_attribute(a,period) for a in attrs]


Creating an event callback

# The callback must be a callable or an object with a push_event(self,event) method

Configuring an event

#From the client side
#subscribe_event(attr_name, event_type, cb_or_queuesize, filters=[], stateless=False, extract_as=PyTango._PyTango.ExtractAs.Numpy)
event_id = PyTango.DeviceProxy.subscribe_event(attributeName,PyTango.EventType.CHANGE,callback_function,[],True)

#From inside the device server

Pushing the event


Device Server Internal Objects

Forcing in which host the device is exported

This environment variable must be set before launching the device:

user@bash:/> export OMNIORB_USEHOSTNAME=

Creating a Device Server from ipython

Having defined your device in

1: from MyDS import *
2: py = PyTango.PyUtil(['','InstanceName'])
3: py.add_TgClass(MyDSClass,MyDS,'MyDS')
4: U = PyTango.Util.instance()
5: U.server_init()
6: U.server_run()

Get the device server admin


U = PyTango.Util.instance()

Modify internal polling

NOTE: It doesn't work at init_device(); must be done later on in a hook method

U = PyTango.Util.instance()
admin = U.get_dserver_device()

polled_attrs = {}
for st in admin.DevPollStatus(name):
  lines = st.split('\n')
  try: polled_attrs[lines[0].split()[-1]]=lines[1].split()[-1]
  except: pass

type_ = 'command' or 'attribute'
for aname in args:
 if aname in polled_attrs:

Get all polling attributes

The polling of the attributes is recorded in the property_device table of the tango database in the format of a list like [ATTR1,PERIOD1,ATTR2,PERIOD2,...]

The list of polled attributes can be accessed using this method of admin device:

dp = PyTango.DeviceProxy('dserver/myServerClass/id22')
polled_attrs = [a.split('\n')[0].split(' ')[-1] for a in dp.DevPollStatus('domain/family/member-01')]

Get the device class object from the device itself


Get the devices inside a Device Server

    def get_devs_in_server(self,MyClass=None):
        Method for getting a dictionary with all the devices running in this server
        MyClass = MyClass or type(self) or DynamicDS
        if not hasattr(MyClass,'_devs_in_server'):
            MyClass._devs_in_server = {} #This dict will keep an access to the class objects instantiated in this Tango server
        if not MyClass._devs_in_server:
            U = PyTango.Util.instance()
            for klass in U.get_class_list():
                for dev in U.get_device_list_by_class(klass.get_name()):
                    if isinstance(dev,DynamicDS):
        return MyClass._devs_in_server

Identify each attribute inside read_attr_hardware()

    def read_attr_hardware(self,data):
        self.debug("In DynDS::read_attr_hardware()")
            attrs = self.get_device_attr()
            for d in data:
                a_name = attrs.get_attr_by_ind(d).get_name()
                if a_name in self.dyn_attrs:
                    self.lock.acquire() #This lock will be released at the end of read_dyn_attr
                    self.myClass.DynDev=self #VITAL: It tells the admin class which device attributes are going to be read
                    self.lock_acquired += 1
            self.debug('DynamicDS::read_attr_hardware(): lock acquired %d times'%self.lock_acquired)
        except Exception,e:
            self.last_state_exception = 'Exception in read_attr_hardware: %s'%str(e)
            self.error('Exception in read_attr_hardware: %s'%str(e))    

Device server logging (using Tango logs)



debug_stream ( str )

info_stream ( str )

warning_stream ( str )

error_stream ( str )

fatal_stream ( str )

Or use fandango.Logger object instead ...

Adding dynamic attributes to a device

     PyTango.Attr( #or PyTango.SpectrumAttr
             new_attr_name,PyTango.DevArg.DevState,PyTango.AttrWriteType.READ, #or READ_WRITE
             #max_size or dyntype.dimx #If Spectrum
     self.read_new_attribute, #(attr)
     None, #self.write_new_attribute #(attr)
     self.is_new_attribute_allowed, #(request_type)

Using Database Object

import PyTango
db = PyTango.Database()

Register a new device server

dev = 'SR%02d/VC/ALL'%sector
klass = 'PyStateComposer'
server = klass+'/'+dev.replace('/','_')

di = PyTango.DbDevInfo(),di._class,di.server = device,klass,server

Remove "empty" servers from database

tango = PyTango.Database()
   for s in tango.get_server_list() 
   if all(d.lower().startswith('dserver') for d in tango.get_device_class_list(s))

Force unexport of a failing server

You can check using db object if a device is still exported after killed

In [40]:bool(db.import_device('dserver/HdbArchiver/11').exported)

You can unexport this device or server with the following call:


It would normally allow you to restart the server again.

Get all servers of a given class

class_name = 'Modbus'
list_of_names = ['/'.join((class_name,name)) for name in db.get_instance_name_list(class_name)]

Differences between DB methods:

  • get_instance_name_list(exec_name): return names of instances
  • get_server_list(): returns list of all executable/instance
  • get_server_name_list(): return names of all executables

Get all devices of a server or a given class

The command is:

  • db.get_device_class_list(server_name): return ['device/name/family','device_class']*num_of_devs_in_server

The list returned includes the admin server (dserver/exec_name/instance) that must be pruned from the result:

list_of_devs = [dev for dev in db.get_device_class_list(server_name) if '/' in dev and not dev.startswith('dserver')]

Get all devices of a given class from the database

import operator
list_of_devs = reduce(operator.add,(list(dev for dev in db.get_device_class_list(n) \
   if '/' in dev and not dev.startswith('dserver')) for n in \
   ('/'.join((class_name,instance)) for instance in db.get_instance_name_list(class_name)) \

Get property values for a list of devices

  • db.get_device_property_list(device_name,'*') : returns list of available properties
  • db.get_device_property(device_name,[property_name]) : return {property_name : value}
prop_names = db.get_device_property_list(device_name)
dev_props = db.get_device_property(device_name,prop_names)
   {'property1':'first_value' , 'property2':'second_value' }

Get the history (last ten values) of a property

In [188]: [ph.get_value().value_string for ph in tango.get_device_property_history('some/alarms/device','AlarmsList')]

[['MyAlarm:a/gauge/controller/Pressure>1e-05', 'TempAlarm:a/nice/device/Temperature_Max > 130'],

Get the server for a given device

>>> print db.get_server_list('Databaseds/*')
>>> print db.get_device_name('DataBaseds/2','DataBase')
>>> db_dev=PyTango.DeviceProxy('sys/database/2')
>>> print db_dev.command_inout('DbImportDevice','et/wintest/01')
([0, 2052], ['et/wintest/01', 'IOR:0100000017000xxxxxx', '4', 
'WinTest/manu', '', 'WinTest'])

Get the Info of a not running device (exported, host, server)

def get_device_info(dev):
    vals = PyTango.DeviceProxy('sys/database/2').DbGetDeviceInfo(dev)
    di = dict((k,v) for k,v in zip(('name','ior','level','server','host','started','stopped'),vals[1]))
    di['exported'],di['PID'] = vals[0]
    return di

Set property values for a list of devices

Attention , Tango property values are always inserted as lists! {property_name : [ property_value ]}

prop_name,prop_value = 'Prop1','Value1'
[db.put_device_property(dev,{prop_name:[prop_value]}) for dev in list_of_devs]

Get Starter Level configuration for a list of servers

[(,si.mode,si.level) for si in [db.get_server_info(s) for s in list_of_servers]]

Set Memorized Value for an Attribute


Useful constants and enums

In [31]:PyTango.ArgType.values
{0: PyTango._PyTango.ArgType.DevVoid,
 1: PyTango._PyTango.ArgType.DevBoolean,
 2: PyTango._PyTango.ArgType.DevShort,
 3: PyTango._PyTango.ArgType.DevLong,
 4: PyTango._PyTango.ArgType.DevFloat,
 5: PyTango._PyTango.ArgType.DevDouble,
 6: PyTango._PyTango.ArgType.DevUShort,
 7: PyTango._PyTango.ArgType.DevULong,
 8: PyTango._PyTango.ArgType.DevString,
 9: PyTango._PyTango.ArgType.DevVarCharArray,
 10: PyTango._PyTango.ArgType.DevVarShortArray,
 11: PyTango._PyTango.ArgType.DevVarLongArray,
 12: PyTango._PyTango.ArgType.DevVarFloatArray,
 13: PyTango._PyTango.ArgType.DevVarDoubleArray,
 14: PyTango._PyTango.ArgType.DevVarUShortArray,
 15: PyTango._PyTango.ArgType.DevVarULongArray,
 16: PyTango._PyTango.ArgType.DevVarStringArray,
 17: PyTango._PyTango.ArgType.DevVarLongStringArray,
 18: PyTango._PyTango.ArgType.DevVarDoubleStringArray,
 19: PyTango._PyTango.ArgType.DevState,
 20: PyTango._PyTango.ArgType.ConstDevString,
 21: PyTango._PyTango.ArgType.DevVarBooleanArray,
 22: PyTango._PyTango.ArgType.DevUChar,
 23: PyTango._PyTango.ArgType.DevLong64,
 24: PyTango._PyTango.ArgType.DevULong64,
 25: PyTango._PyTango.ArgType.DevVarLong64Array,
 26: PyTango._PyTango.ArgType.DevVarULong64Array}

In [30]:PyTango.AttrWriteType.values
{0: PyTango._PyTango.AttrWriteType.READ,
 1: PyTango._PyTango.AttrWriteType.READ_WITH_WRITE,
 2: PyTango._PyTango.AttrWriteType.WRITE,
 3: PyTango._PyTango.AttrWriteType.READ_WRITE}

In [29]:PyTango.AttrWriteType.values[3] is PyTango.READ_WRITE

Using Tango Groups

This example uses PyTangoGroup? to read the status of all devices in a Device Server

import PyTango

server_name = 'VacuumController/AssemblyArea'
group = PyTango.Group(server_name)
devs = [d for d in PyTango.Database().get_device_class_list(server_name) if '/' in d and 'dserver' not in d]
for d in devs:

answers = group.command_inout('Status',[])
for reply in answers:
    print 'Device %s Status is:' % reply.dev_name()
    print reply.get_data()

About Exceptions

Be aware that I'm not sure about all of this:

                 "Last communication failed at %s, waiting %s millis"%(time.ctime(self.last_failed),self.ErrorTimeWait),
except PyTango.DevFailed,e:
  if e.args[0]['reason']!='API_AsynReplyNotArrived':
     PyTango.Except.re_throw_exception(e,"DevFailed Exception",str(e),inspect.currentframe().f_code.co_name)

Passing Arguments to Device command_inout

When type of Arguments is special like DevVarLongStringArray the introduction of arguments is something like:

In [25]:api.manager.command_inout('UpdateSnapComment',[[40],['provant,provant...']])

Using asynchronous commands

cid = self.modbus.command_inout_asynch(command,arr_argin)
while True:
    self.debug('Waiting for asynchronous answer ...')
        result = self.modbus.command_inout_reply(cid)
        self.debug('Received: %s' % result)
    except PyTango.DevFailed,e:
        self.debug('Received DevFailed: %s' %e)
        if e.args[0]['reason'] != 'API_AsynReplyNotArrived':
           raise Exception,'Weird exception received!: %s' % e

Setting Attribute Config

for server in astor.values():
        for dev in server.get_device_list():
                dp = server.get_proxy(dev)
                attrs = dp.get_attribute_list()
                if dev.rsplit('/')[-1].lower() not in [a.lower() for a in attrs]: continue
                conf = dp.get_attribute_config(dev.rsplit('/')[-1])
                conf.format = "%1.1e"
                conf.unit = "mbar"
                conf.label = "%s-Pressure"%dev
                print 'setting config for %s/%s' % (dev,

Porting device servers to PyTango7

The changes to easily port PyTango?<7 devices are:

If you are quite lazy you can add this at the beginning of your $ file (and be still parseable by Pogo):

import PyTango
if 'PyUtil' not in dir(PyTango): 
    PyTango.Device_3Impl = PyTango.Device_4Impl
    PyTango.PyDeviceClass = PyTango.DeviceClass
    PyTango.PyUtil = PyTango.Util

Simplify changes by adding this line

if 'PyUtil' not in dir(PyTango): 
    PyTango.PyDeviceClass = PyTango.DeviceClass
    PyTango.PyUtil = PyTango.Util
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