How to detect changes in firebase child with python?

Question

I have some troubles with this application. What I need is that If I detect a change in the database (FIREBASE) particularly in \'sala\' and \'ventilacion\' nodes the functi

Answer 1

I was working on the same thing so according to current updates on pyrebase and learning from above posted answers, I got this running perfectly.(Please make sure your python is upgraded from python2 to python3 for running pyrebase and firebase-admin)

import firebase_admin
import pyrebase
from firebase_admin import credentials

config = {
    "apiKey": "",
    "authDomain": "",
    "databaseURL": "",
    "projectId": "",
    "storageBucket": "",
    "serviceAccount": "path to the service account json file you downloaded",
    "messagingSenderId": "",
    "appId": "",
    "measurementId": ""
}

firebase = pyrebase.initialize_app(config)
storage = firebase.storage()
cred = credentials.Certificate("path to downloaded json file")

firebase_admin.initialize_app(cred, {
    "databaseURL": "same as config",
    "databaseAuthVariableOverride": None
})
db = firebase.database()

def ignore_first_call(fn):
    called = False

    def wrapper(*args, **kwargs):
        nonlocal called
        if called:
            return fn(*args, **kwargs)
        else:
            called = True
            return None
    return wrapper

def stream_handler(message):
    ab = str(1)
    all_videos = storage.child("videos/").list_files() #node where files are

    path_on_local = "local path to save the downloads"
    print(message["event"]) # put
    print(message["path"]) # /-K7yGTTEp7O549EzTYtI
    print(message["data"]) # {'title': 'Pyrebase', "body": "etc..."}

    node = str(message["path"]).split('/')[-2] 
    property = str(message["path"]).split('/')[-1]
    value = message["data"]

    if (message["event"] == "put"):
        for videos in all_videos:
            try:
                print(videos.name)
                z = storage.child(videos.name).get_url(None)
                storage.child(videos.name).download(path_on_local + "/" + ab + ".mp4")
                x = int(ab)
                ab = str(x + 1)
            except:
                print('Download Failed')

    else:
        print("error")

my_stream = db.child("videos").stream(stream_handler)

Answer 2

Question: How to detect changes in firebase child

---

Note: All Examples use Public Access

1. Setup Example Data and verify it's readable.
   This hase to be done once!

   temperature_c = 30
   data = {'date':time.strftime('%Y-%m-%d'), 
           'time':time.strftime('%H:%M:%S'), 
           'temperature':temperature_c}
   db.child('public').child('Device_1').set(data)
   
   response = db.child('public').child('Device_1').get()
   print(response.val())
   

2. Create First Script doing Updates:

   for t in [25, 26, 27, 28, 29, 30, 31, 32, 33, 35]:
       temperature_c = t
       data = {'date':time.strftime('%Y-%m-%d'), 
               'time':time.strftime('%H:%M:%S'), 
               'temperature':temperature_c}
       db.child('public').child('Device_1').update(data)
       time.sleep(60)
   

3. Create Second Script with Stream Handler

   def stream_handler(message):
       print('event={m[event]}; path={m[path]}; data={m[data]}'
           .format(m=message))
   
   my_stream =db.child('public').child('Device_1').stream(stream_handler)
   
   # Run Stream Handler forever
   while True:
       data = input("[{}] Type exit to disconnect: ".format('?'))
       if data.strip().lower() == 'exit':
           print('Stop Stream Handler')
           if my_stream: my_stream.close()
           break
   

4. Run Stream Handler Script:

   Response Output from def stream_handler after startup (Initial Data):

   event="put"; path=/;  data={'Device_1': {'temperature': 30, 'time': '13:34:24', 'date': '2017-07-20'}}
   

5. Run Updater Script:

6. Watch Output from Stream Handler Script

   Response Output from def stream_handler after First Update Data:

   event=patch; path=/Device_1;  data={'temperature': 25, 'time': '13:49:12'}
   

Tested with Python: 3.4.2

---

Pyrebase
streaming

You can listen to live changes to your data with the stream() method.

def stream_handler(message):
    print(message["event"]) # put
    print(message["path"]) # /-K7yGTTEp7O549EzTYtI
    print(message["data"]) # {'title': 'Pyrebase', "body": "etc..."}

my_stream = db.child("posts").stream(stream_handler)

You should at least handle put and patch events. Refer to "Streaming from the REST API" for details.

Answer 3

I know this post is 2 years old but hope this helps. Try using firebase_admin module.

Use this command - pip install firebase-admin

I too had a requirement where I needed to check for changes made to the Firebase database. I referred here

Following is a sample code based on your question which you can refer from and try it out.

import firebase_admin
from firebase_admin import credentials
from firebase_admin import db


cred = credentials.Certificate("path/to/serviceAccountKey.json")
firebase_admin.initialize_app(cred, {
    'databaseURL': 'https://example.firebaseio.com',
    'databaseAuthVariableOverride': None
})


def ignore_first_call(fn):
    called = False

    def wrapper(*args, **kwargs):
        nonlocal called
        if called:
            return fn(*args, **kwargs)
        else:
            called = True
            return None

    return wrapper


@ignore_first_call
def listener(event):
    print(event.event_type)  # can be 'put' or 'patch'
    print(event.path)  # relative to the reference, it seems
    print(event.data)  # new data at /reference/event.path. None if deleted

    node = str(event.path).split('/')[-2] #you can slice the path according to your requirement
    property = str(event.path).split('/')[-1] 
    value = event.data
    if (node=='sala'):
        #do something
    elif (node=='ventilacion'):
        #do something
    else:
        #do something else


db.reference('/').listen(listener)