Python client for lightstreamer

Colombao

Hi All, I would like to ask if anyone can provide a basic Python Client example.

I think a very basic and useful example could be a Python code that display push received time/date of the example http://demos.lightstreamer.com/HelloWorld/ .

I already red the Generic Protocol Documentation, I'm able to create the createsession.txt url but it doesn't refresh in my code (push doesn't work).

I searched a lot in web, but I didn't find any that could clarify this (https://github.com/dw/py-lightstreamer actually doesn't works and/or there isn't a documentation).

I have last Python, 3.4

Any help will be appreciated.
Thanks and br.

Alessandro Alinone

Hi Colombao,

I'm not aware of more recent ready-made examples for Python.

If you start from https://github.com/dw/py-lightstreamer (which was not developed by us) and let us know what is not working, we can support you in fixing any issue with the Lightstreamer protocol.

Thanks,
Alessandro

Colombao

Hi Alessandro, many thanks for your quick feedback. Frankly speaking, I don't know how to proceed after "import lightstreamer" (the example included in the library web page, "barebones.py" gives a lot of different error that make me feel that there is something completely wrong from the base).

If anyone of Lighstreamer team could know how to do a client in python, I think a very basic, useful and "end to end" example could be a Python code that display push received time/date of the example http://demos.lightstreamer.com/HelloWorld/ .

Please note that I converted the original lightstreamer library to be compatible with python 3.4 one, using Python 2to3 converter. Maybe something went wrong during conversion. An hypothesis could be that the library is not convertible but compatible only with Python 2.7, but even in this case I don't have an example of how use that library.

Anyone can help me?
Thanks and best regards,
Colombao

Alessandro Alinone

Colombao,

Thanks for the suggestion. A quick Python client example does make sense, so that we can add it to our demo database: http://demos.lightstreamer.com/

We will try to work on it over the next few weeks and publish it on GitHub. We'll let you know.

Cheers,
Alessandro

Colombao

Hi Alessandro,
thanks again for you help. Since Python is more a "mathematical" language than an "Interface" one, in my honest opinion it could be enough to print received data directly into standard output (eg. using "print()" ), without the necessity of developing a real interface, for which there are more appropriate languages. I'll follow this thread!

Thanks again!
Colombao

Alessandro Alinone

Ok, will use printf() to keep the example as simple as possible.
Thanks

Gianluca Finocchiaro

We have just released on GitHub a simple Python script that shows a minimal client-side implementation of the Lightstreamer Server Text mode Protocol.
https://github.com/Weswit/Lightstreamer-example-StockList-client-python

Jim

Thanks gianluca.finocchiaro. It looks like that demo is featured on the Lightstreamer demo page now.

When I execute the script, I get a syntax error. Any idea why? I'm running Python 2.6.

>python stock_list_demo.py
File "stock_list_demo.py", line 92
k: self._decode(v, curr_item.get(k)) for k, v
^
SyntaxError: invalid syntax

Jim

Dictionary comprehensions are not supported in python 2.6. You need to use 2.7 to run this. You may want to update your requirements to say 2.7 instead of any 2.x version.

Gianluca Finocchiaro

Hi Jim.

thanks for reporting this issue. I have just the fixed backward compatibility with Python 2.6, now available on GitHub.
Let me know for any further problem.

Regards,
Gianluca

Colombao

Hi All, I tried in 2 different PCs running:
- Windows 7
- Python 2.7.8
- Java jdk1.8.0_25
but I receive the following error:

ERROR:root:Server response error: <!--
Unable to connect to Lightsreamer Server

while the server is running, I can confirm that I can see push data using browser at [url]http://localhost:xxxx[/url]

any suggestion?

Thanks and br

Gianluca Finocchiaro

Hi,

I've just uploaded a new version with improved error logs, in order to print out the complete server response.
In the meantime, could you please tell us which version of Lightstreamer Server you are currently using?

Regards,
Gianluca

Gianluca Finocchiaro

Moreover, be aware that the demo does not work with the Moderato Edition, as stated in the Compatibility Notes you can find here.

Let me know.

Thanks and Regards,
Gianluca

Colombao

Ciao Gianluca!
many thanks for your help, following your suggestion
- I downloaded Lightstreamer Allegro/Presto/Vivace Editions at http://download.lightstreamer.com/
- I installed the deploy of stocklist demo at https://github.com/Weswit/Lightstreamer-example-StockList-adapter-java/releases (unzip and copying the folder into <LS path>\adapters\Demo\stocklist
- I aligned Java version with the mine : set JAVA_HOME=C:\Program Files\Java\jdk1.8.0_25 of file LS.bat in <LS path>\bin\windows
- I lauched Start_LS_as_Application.bat
- successfully checked that via browser at http://localhost:8789/demos/StockListDemo/push stock data are displayed (I randomly choose 8789 as port, I aligned the port into conf file : <port>8789</port> of file lightstreamer_conf.xml )
- from the python IDLE, I run the code without any modification except the port at
lightstreamer_client = LSClient("http://localhost:8789", "DEMO")

now I see the following:

Python 2.7.2 (default, Jun 12 2011, 14:24:46) [MSC v.1500 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>>
------------HIT CR TO UNSUBSCRIBE AND DISCONNECT FROM LIGHTSTREAMER-------------

(no new lines after this one, I waited ~10 minutes)

I have
- Windows 7 64bit
- Python 2.7.8
- Java jdk1.8.0_25

I'm available for further tests, any help or hint will be appreciated

Thanks and br

Colombao

ok, after further tests I have an update, it doesn't work if I lauch it from IDLE, otherwise it works if I launch it directly from cmd or simply clicking on the icon. Many thanks!

Gianluca Finocchiaro

Hi,

I admit I didn't test the script from the Python IDLE. It actually shows a strange behavior, I suppose due to the raw_input() function: if you hit cr just after running the code you can see all the updates printing out on the console, then the script ends. I will investigate on this. Many thanks for reporting such bizarre issue!

Regards,
Gianluca

Colombao

Hi Gianluca, as requested on IG forum here, I post here the issue I faced while trying to develop an LS python client for IG.com API :

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hi Gianluca, many thanks for your code. It works perfectly with LighStreamer Stock_List_Demo but for me it doesn't with IG LS server.
I modified your code in order to be used with IG : http://www.yourfilelink.com/get.php?fid=1018265
Instruction
1) login into http://labs.ig.com/sample-apps/api-companion/index.htmlwith a DEMO account and copy CST, XST e account name
2) modify lines 313-318 updating values
EXAMPLE:
############################################################################
############### SECTION TO BE UPDATED USING DATA PROVIDED BY REST TRADING API
cst = 'c39bccbe6e63b808606717650b7d60dfdf164344af2f0e07e2e5640d8721a24301111'
xst = '9959426da3f4a889a21c3ec43c7b863f9488a780e6e41e898003645a38fe4bb201111'
usr = "XAGUS"
#############################################################################
3) update lines 337-340 with an Item and a field (as indicated in https://labs.ig.com/streaming-api-reference) :
EXAMPLE:
subscription = Subscription( mode="MERGE",
adapter="",
items=["CHART:CS.D.EURJPY.CFD.IP:TICK"],
fields= ['OFR'])
4) save and run the code
It connects to LS server but I don't see any update after "HIT CR TO UNSUBSCRIBE AND DISCONNECT FROM LIGHTSTREAMER"...
I'm doing something wrong?
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Many thanks for your quick support and best regards!

Gianluca Finocchiaro

Hi Colombao,

are you executing the code from IDLE or from command line?

Gianluca

Colombao

Hi Gianluca, I tried both. Does it work for you with step I provided?

Best regards

Colombao

Hi Gianluca, i suggest you to use following schema, because I'm quite sure that it should work with IG

item_ids='MARKET:CS.D.GBPUSD.CFD.IP',
schema='UPDATE_TIME BID OFFER CHANGE MARKET_STATE'

I sent you a private message with my credentials. Thanks and br