subprocess stdout into a variable for Ngrok

Question

I'm trying to make a python script wich reports me the port on 0.tcp.ngrok.io is started when I run the code on terminal (after moving ngrok executable file to /usr/local/bin)

ngrok tcp 22

I get ths kind of output

ngrok by @inconshreveable                                       (Ctrl+C to quit)

Session Status                connecting                                        
Version                       2.2.4                                             
Region                        United States (us)                                
Web Interface                 http://127.0.0.1:4041                             
Forwarding                    tcp://0.tcp.ngrok.io:13014 -> localhost:22                                                                                 
Connections                   ttl     opn     rt1     rt5     p50     p90       
                              0       0       0.00    0.00    0.00    0.00  

My first attempt is to log the subprocess stdout to a variable , but as the stdout is cyclic the stdout.read() never ends this is the code

import subprocess

ngrok = subprocess.Popen(['ngrok','tcp','22'],stdout = subprocess.PIPE)

output_text = ngrok.stdout.read() # script stops here forever

[**code for getting domain:port from output_text**]

how can I get a "snapshot" of stdout to a variable , without stoping ngrok?

Is there another way of doing this (next try would be a webscrapper on localhost , but it would be nice to have this knowledge for other commands , such as "top")

thanks in advance