Subscribe to spark events using python

Cloud
1

Hi,

I wrote a small python program that control my spark from my computer. I would like to read spark events.
I found it pretty easy to call functions and read variables, but didn’t figure out how to read events. I also failed to find someone who implement reading spark events with python.

Spyrk is a great project, but unfortunately not support Spark event for now.
SSEclient is Python library enable Server sent event but when I try to use it I get ‘400 - bad request’ from Spark cloud.

What is the right way to read spark event with Python client?

2

Looking at the example for SSEClient:

from sseclient import SSEClient

messages = SSEClient('http://mysite.com/sse_stream/')
for msg in messages:
    do_something_useful(msg)

What’s the URL that you used?

It should be something like this: https://api.spark.io/v1/events?access_token=4fcab3c6ea4ce95e8e7c

1 Like
3

Using python 2.7:

from sseclient import SSEClient 
import requests, json

messages = SSEClient('https://api.spark.io/v1/events/{EVENT FILTER}?access_token={ACCESS TOKEN}')

for msg in messages:
    event = str(msg.event).encode('utf-8')
    data = str(msg.data).encode('utf-8')
    print event
    print data
    dataJson = json.loads(data)
4

I'm trying to parse simple data from DHT22 temperature humidity sensor from an event stream but with the code above I keep getting
File "/usr/lib/python2.7/json/init.py", line 338, in loads
return _default_decoder.decode(s)
File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode
raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

and if I # out the dataJson line and just print the raw event and data I get:

Humidity-office
{"data":"48.099998","ttl":"60","published_at":"2016-08-21T03:27:03.830Z","coreid":"360033001747343338333633"}
Temperature-office
{"data":"26.799999","ttl":"60","published_at":"2016-08-21T03:27:03.851Z","coreid":"360033001747343338333633"}

which and the data looks like good json... but I'm a newbie

6

I’m not a Python guy, but how about removing the event name first and only providing the JSON part of data to the decoder?

7

This is an old thread but thought I’d add my code in case someone else runs into the same issue. It took me a few hours to figure out. Maybe someone will find it useful and save them time.

#prior code omitted from this post cleanliness
for msg in messages:
    
    #Get the message event type. This is the Publish Event name. 
    event = str(msg.event)

    #Only add events to SQL that have the event name of "Stat"
    if event == 'Stat':

        #use str and JSON.Loads to decifer string/JSON object from Particle into a Python Dictionary
        data = str(msg.data)
        msgDict = json.loads(data)
        dataDict = json.loads(msgDict["data"])
        msgDict.update({'data': dataDict})

        #Now that the message from Particle is a Pyhton Dictionary, access info within it like this:
        DEVICE_ID=msgDict["coreid"], 
        TempF=msgDict['data']['TempF'] 

        #Do whatever you want with the data now.