Develop Reference

Linking Power BI with Python to download Reports and send it to a whatsApp contact

The problem statement I have in hand is, I am trying to automate the process of downloading reports from Power BI and send it to the various WhatsApp contacts with the help of Python.
Is this possible?
I found the Microsoft REST APIs which can be used to download the reports but I am getting lost in trying to configure my credentials and other things.

Check the reply in the following case Power BI API - How can I get reports from app.powerbi.com?
If you want to do this using an API, you will need Export Report In Group REST API. To use it, you need to acquire an access token and add it to your request header. You can acquire it by calling some of the AcuireToken methods from ADAL.
You can use code like this (please note there is no error checking in the example):
string clientId = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"; // Obtain at https://dev.powerbi.com/apps
string redirectUri = "https://login.live.com/oauth20_desktop.srf";
string resourceUri = "https://analysis.windows.net/powerbi/api";
string authorityUri = "https://login.windows.net/common/oauth2/authorize";
AuthenticationContext authContext = new AuthenticationContext(authorityUri, new TokenCache()); // PM> Install-Package Microsoft.IdentityModel.Clients.ActiveDirectory
var authenticationResult = await authContext.AcquireTokenAsync(resourceUri, clientId, new Uri(redirectUri), new PlatformParameters(PromptBehavior.Auto));
var accessToken = authenticationResult.AccessToken);
string powerBIApiUrl = "https://api.powerbi.com/v1.0/myorg/groups/{groupId}/reports/{reportKey}/Export"; // Replace groupId and reportKey with actual values
var request = WebRequest.Create(powerBIApiUrl) as HttpWebRequest;
request.KeepAlive = true;
request.Method = "GET";
request.ContentLength = 0;
request.ContentType = "application/json";
request.Headers.Add("Authorization", $"Bearer {accessToken}");
using (HttpWebResponse httpResponse = request.GetResponse() as System.Net.HttpWebResponse)
{
//Read httpResponse.GetResponseStream() to get the .pbix file
}
Also, there are other useful links:
https://community.powerbi.com/t5/Developer/Power-BI-REST-API-using-postman-generate-embed-token/m-p/310153#M9157
https://www.sqlshack.com/how-to-access-power-bi-rest-apis-programmatically/

How do i use GraphSON v2 instead of v3?

i am trying to run a piece of code in python which uses Cosmos DB from Microsoft Azure. I am currently using gremlinpython 3.2.6 and the latest version of Cosmos (default on microsoft azure) but there seems to be some compatibility issues between the two.
When i run my code i get the following error;
GremlinServerError: 498:
ActivityId : 5c05bb15-3aa1-41b8-9c10-ab3015152eab
ExceptionType : GraphMalformedException
ExceptionMessage :
Gremlin Malformed Request: GraphSON v3 IO is not supported.
GremlinRequestId : 5c05bb15-3aa1-41b8-9c10-ab3015152eab
Context : global
GraphInterOpStatusCode : MalformedRequest
HResult : 0x80131500
I have read that I should try using GraphSON v2 instead of V3 but don't know how, can anyone help?

welcome to this community. You just need to ensure that you use the schema of the GraphSON v2, since it is the version supported in Azure Cosmos DB. Check the json you are using and ensure that follows the supported schema. You have some examples in this link.

Using C#, If you put your connection config in Startup.cs you can configure it like this:
services.AddSingleton<GremlinClient>(
(serviceProvider) =>
{
var gremlinServer = new GremlinServer(
hostname: "<account>.gremlin.cosmosdb.azure.com",
port: <port>,
enableSsl: true,
username: "/dbs/<db>/colls/<collection>",
password: ""
);
var connectionPoolSettings = new ConnectionPoolSettings
{
MaxInProcessPerConnection = 32,
PoolSize = 4,
ReconnectionAttempts = 3,
ReconnectionBaseDelay = TimeSpan.FromSeconds(1),
};
var mimeType = "application/vnd.gremlin-v2.0+json";
return new GremlinClient
(
gremlinServer: gremlinServer,
graphSONReader: new GraphSON2Reader(),
graphSONWriter: new GraphSON2Writer(),
mimeType: mimeType,
connectionPoolSettings: connectionPoolSettings
);
}
);
Otherwise you should create the gremlin client with the following reader, writer and mimeType:
var mimeType = "application/vnd.gremlin-v2.0+json";
var client = new GremlinClient
(
gremlinServer: <your server>,
graphSONReader: new GraphSON2Reader(),
graphSONWriter: new GraphSON2Writer(),
mimeType: mimeType,
connectionPoolSettings: <your connection pool>
);

By default gremlin_python uses the GraphSONSerializersV3d0, so you have to explicitly pass the GraphSONSerializersV2d0 when creating the client:
from gremlin_python.driver import client, serializer
client.Client(
message_serializer=serializer.GraphSONSerializersV2d0(),
password="...",
traversal_source='g',
url='wss://...:443/',
username="/dbs/.../colls/...",
)

Provide it as mime type when you create client
var client = new GremlinClient(gremlinServer:gremlinServer,mimeType:GremlinClient.GraphSON2MimeType)

You need to downgrade the version to the supported connector version. This applies to all programming languages. For python as of this writing, it is 3.2.7.

Firestore: Listen to documents in a subcollection

I am trying to listen to documents in collection from Python code using example from Firestore Documentation. I receive correct data when listening root collection, but got nothing when listening subcollection.
Here's my code:
db = firestore.client()
# Create a callback on_snapshot function to capture changes
def on_snapshot(col_snapshot, changes, read_time):
print(col_snapshot, type(col_snapshot))
print(changes, type(col_snapshot))
root_collection = u'shared-streams'
subcollection = u'shared-streams/eFC4T~lLyT/messages'
# Watch the root collection query (1)
col_query = db.collection(root_collection)
query_watch = col_query.on_snapshot(on_snapshot)
# Watch the subcollection query (2)
col_query = db.collection(subcollection)
query_watch = col_query.on_snapshot(on_snapshot)
Subcollection exists in Firestore and non-empty. But in first case (1) I got non-empty lists of elements and changes (and updates), and in other case (2) just two empty lists (and nothing when update subcollection). As I know there are no differences in root/sub- collections, so, please, explain where am I wrong.
UPD: Similar code in node.js works fine, so looks like it is error in python client library.
node.js snippet:
var db = admin.firestore();
var query = db.collection('shared-streams/eFC4T~lLyT/messages')
var observer = query.onSnapshot(querySnapshot => {
console.log(`Received query snapshot of size ${querySnapshot.size}`);
// ...
}, err => {
console.log(`Encountered error: ${err}`);
});

Connecting Python Backend to Android APP

How to use python as a backend for an Android App that is built using C#? The Python Backend is written using the Flask framework. The Android app is built using xamarin.

No matter what type of technology your server or the client use if they can communicate with each other using some sort of standard "protocol".
There are many ways to communicate both sides (client and server) like sockets, xml, json, etc. They just need to understand each other.
In your particular case I suggest to build a REST or RESTful API (https://flask-restful.readthedocs.org/en/0.3.3/) on the server and a REST client library on the client.
There are many ways and libraries to call REST APIs from C#:
The built-in method would be using HttpWebRequest as you can see on this link:
private async Task<JsonValue> FetchWeatherAsync (string url)
{
// Create an HTTP web request using the URL:
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create (new Uri (url));
request.ContentType = "application/json";
request.Method = "GET";
// Send the request to the server and wait for the response:
using (WebResponse response = await request.GetResponseAsync ())
{
// Get a stream representation of the HTTP web response:
using (Stream stream = response.GetResponseStream ())
{
// Use this stream to build a JSON document object:
JsonValue jsonDoc = await Task.Run (() => JsonObject.Load (stream));
Console.Out.WriteLine("Response: {0}", jsonDoc.ToString ());
// Return the JSON document:
return jsonDoc;
}
}
}
But I don´t recommend it if you don´t want your app to be full of crap (boiler plate code) everywhere.
A helper library could be, for example, RESTSharp. It allows you to build REST calls easily and cast the response to your typed objects. Here´s and example:
var client = new RestClient("http://example.com");
// client.Authenticator = new HttpBasicAuthenticator(username, password);
var request = new RestRequest("resource/{id}", Method.POST);
request.AddParameter("name", "value"); // adds to POST or URL querystring based on Method
request.AddUrlSegment("id", "123"); // replaces matching token in request.Resource
// easily add HTTP Headers
request.AddHeader("header", "value");
// add files to upload (works with compatible verbs)
request.AddFile(path);
// execute the request
RestResponse response = client.Execute(request);
var content = response.Content; // raw content as string
// or automatically deserialize result
// return content type is sniffed but can be explicitly set via RestClient.AddHandler();
RestResponse<Person> response2 = client.Execute<Person>(request);
var name = response2.Data.Name;
// easy async support
client.ExecuteAsync(request, response => {
Console.WriteLine(response.Content);
});
// async with deserialization
var asyncHandle = client.ExecuteAsync<Person>(request, response => {
Console.WriteLine(response.Data.Name);
});
// abort the request on demand
asyncHandle.Abort();
You can search "C# REST client" on google and judge by yourself. But IMHO, the easier and nicer to code REST client I´ve ever used is Refit.
Why? you define API calls and responses with just an interface. No coding required at all! Even more, all your API calls will be async by default, something needed for mobile apps to be responsive. From the author´s readme:
public interface IGitHubApi
{
[Get("/users/{user}")]
Task<User> GetUser(string user);
}
var gitHubApi = RestService.For<IGitHubApi>("https://api.github.com");
var octocat = await gitHubApi.GetUser("octocat");
I´ve used this library on Xamarin Android/iOS projects and it works well. No issues at all.
Hope it helps

How to limit Autobahn python subscriptions on a per session basis

I am using autobahnpython with twisted (wamp) on server side and autobahnjs in browser. Is there a straight-forward way to allow/restrict subscriptions on a per session basis? For example, a client should not be able to subscribe to topics relavant to other users.
While I am NOT using crossbar.io, I tried using the Python code shown in the 'Example' section at the end of this page http://crossbar.io/docs/Authorization/ where a RPC call is first used to give authorization to a client. Of course, I am using my own authorization logic. Once this authorization is successful, I'd like to give the client privileges to subscribe to topics related only to this client, like 'com.example.user_id'. My issue is that even if auth passes, however, I have not found a way to limit subscription requests in the ApplicationSession class which is where the authorization takes place. How can I prevent a client who authorizes with user_id=user_a from subscribing to 'com.example.user_b'?

You can authorize by creating your own router. To do that, subclass Router() and override (at a minumum) the authorize() method:
def authorize(self, session, uri, action):
return True
This method is pretty simple, if you return a True then the session is authorized to do whatever it is attempting. You could make a rule that all subscriptions must start with 'com.example.USER_ID', so, your python code would split the uri, take the third field, and compare it to the current session id, returning True if they match, false otherwise. This is where things get a little weird though. I have code that does a similar thing, here is my authorize() method:
#inlineCallbacks
def authorize(self, session, uri, action):
authid = session._authid
if authid is None:
authid = 1
log.msg("AuthorizeRouter.authorize: {} {} {} {} {}".format(authid,
session._session_id, uri, IRouter.ACTION_TO_STRING[action], action))
if authid != 1:
rv = yield self.check_permission(authid, uri, IRouter.ACTION_TO_STRING[action])
else:
rv = yield True
log.msg("AuthorizeRouter.authorize: rv is {}".format(rv))
if not uri.startswith(self.svar['topic_base']):
self.sessiondb.activity(session._session_id, uri, IRouter.ACTION_TO_STRING[action], rv)
returnValue(rv)
return
Note that I dive into the session to get the _authid, which is bad karma (I think) because I should not be looking at these private variables. I don't know where else to get it, though.
Also, of note, this goes hand in hand with Authentication. In my implementation, the _authid is the authenticated user id, which is similar to a unix user id (positive unique integer). I am pretty sure this can be anything, like a string, so you should be ok with your 'user_b' as the _auth_id if you wish.
-g

I found a relatively simple solution using a Node guest. Here's the code:
// crossbar setup
var autobahn = require('autobahn');
var connection = new autobahn.Connection({
url: 'ws://127.0.0.1:8080/ws',
realm: 'realm1'
}
);
// Websocket to Scratch setup
// pull in the required node packages and assign variables for the entities
var WebSocketServer = require('websocket').server;
var http = require('http');
var ipPort = 1234; // ip port number for Scratch to use
// this connection is a crossbar connection
connection.onopen = function (session) {
// create an http server that will be used to contain a WebSocket server
var server = http.createServer(function (request, response) {
// We are not processing any HTTP, so this is an empty function. 'server' is a wrapper for the
// WebSocketServer we are going to create below.
});
// Create an IP listener using the http server
server.listen(ipPort, function () {
console.log('Webserver created and listening on port ' + ipPort);
});
// create the WebSocket Server and associate it with the httpServer
var wsServer = new WebSocketServer({
httpServer: server
});
// WebSocket server has been activated and a 'request' message has been received from client websocket
wsServer.on('request', function (request) {
// accept a connection request from Xi4S
//myconnection is the WS connection to Scratch
myconnection = request.accept(null, request.origin); // The server is now 'online'
// Process Xi4S messages
myconnection.on('message', function (message) {
console.log('message received: ' + message.utf8Data);
session.publish('com.serial.data', [message.utf8Data]);
// Process each message type received
myconnection.on('close', function (myconnection) {
console.log('Client closed connection');
boardReset();
});
});
});
};
connection.open();