How to dynamically manage a playlist #1043

[carrzkiss]

Back in 2019, tristan-nel asked the question, How to dynamically manage a playlist.
On Mar 2, 2020, he provided the code on how to do it, but for those who have never used Python scripting language, I am at a loss on what to do with it to use it.

This was his final post, and it was cool that he returned and posted it.
===Final Post===
So I ended up using request.dynamic, and using a Python script to request what the next song in the user-managed playlist will be from Cloud Firestore:

In the liquidsoap server:

# Functions
def get_request() =
  uri = list.hd(default="", get_process_lines("python3 request.py"))
  request.create(uri, persistent=true)
end

# Requests
requests = request.dynamic(
  id="requests",
  conservative=false,
  get_request
)

In the Python script:

# ... get the next song info from Firestore
URL = next_song[const.URL]
new_now_playing = now_playing + 1
channel_ref.set({const.NOW_PLAYING : new_now_playing}, merge=True)
print(URL)

===End Final Post===

I am going to guess here on what to do.
I would have to install python3 (After running the below command, it lets me know I don't have it installed.)

liquid@linuxserver: python –version
  Command 'python' not found, did you mean:
  command 'python3' from deb python3
  command 'python' from deb python-is-python3

The Python script would need to be saved as request.py in the same folder as the .liq file.
The code in the liq file is similar to the example code on Request.dynamic.

Will this make it look at the playlist file for new entries, or will you have to do some injection to get the new songs added to the queue?

[vitoyucepi]

python3 should be installed, check python3 --version or python3 -V.

def get_request()
  command = process.quote.command("python3", args=["request.py"])
  uri = list.hd(process.read.lines(command), default="")
  request.create(uri, persistent=true)
end

Also, there is a bug #3134 that could lead to an insatiable hunger mode for request.dynamic.

def get_request()
  command = process.quote.command("python3", args=["request.py"])
  uri =
    try
      list.hd(process.read.lines(command))
    catch _ do
      null()
    end

  null.map(fun(uri) -> request.create(uri, temporary=true), uri)
end

def replaces request.dynamic(%argsof(request.dynamic), callback)
  prevent = ref(false)
  def debounce()
    if prevent() then
      null()
    else
      result = callback()
      if result == null() then
        thread.run({prevent := false}, delay=retry_delay, fast=true)
        prevent := true
      end
      result
    end
  end

  request.dynamic(debounce, %argsof(request.dynamic))
end


requests = request.dynamic(get_request, id="requests", retry_delay=10.)

[carrzkiss]

OK, what are you using for this?
command = process.quote.command("python3", args=["request.py"])
What is your request.py

[vitoyucepi]

I imagined a script that would output requests one per line, separated by \n or \r\n. It can output nothing or exit with a non-zero code if an error occurs.

[carrzkiss]

OK, I have no idea how to do anything like that.

[gAlleb]

Sorry to interfere. But @carrzkiss, are you sure that you need that? How come that you need something without knowing what it is.

If you are not familiar with python, maybe you can implement the required behavior with another language?

request.dynamic is used to manage your music via external scripts (which you have to come up with yourself - it could be php API's or bash scripts or python scripts or even js scripts, you name it) or fetch requests from users. Or like that guy whom you're referring to with this chunk of python script: probably he has made his own solution with Google's Firestore database - but who knows how or what... Do you use Google's Firestore?

To play your music from playlists you can use playlist operator (which is basically a function with request.dynamic in it already). And what does it do? Dynamically requests tracks from a file with lines in it - your playlist. When you make new entries in your file or edit it - playlist would be reloaded if it's not remote one. For remote one you've been given solutions like reload either with rounds or within time interval.

There is a wonderful book - https://www.liquidsoap.info/book/book.pdf which describes in detail the logic of liquidsoap. While some part of it is more tech-specific, another one is very very easy to comprehend which could help you to build up your station in a way you want.

In regards to the script, that Vito has given you - it is a wonderful LS solution to make request to... something and avoid errors or crashing. But you have to understand that this something has to be existent and be written for Vito's function to obtain it.

[carrzkiss]

Thanks, Stefan.
I am going to get up to speed on what the Python script does and how to use it.
I am thinking of creating another channel and testing out the script tristan-nel provided.
Once I find out what it does and how to properly use it.

I love learning new things and have messed around with Python, but that was about 20 years ago. I have not needed it since then, so I have not learned more about it. But I know that it is used in many products that may come in useful for me in the future, especially with the radio station site, so minus well learn what I need to know to get the job done.

Once I can grasp the other script, I will revisit Vito's script here.

[carrzkiss]

vitoyucepi
I am now getting the chance to get back into this project again, after months away from it.

On this part here.
command = process.quote.command("python3", args=["request.py"])

You stated.

I imagined a script that would output requests one per line,
separated by \n or \r\n. It can output nothing or exit with a non-zero code if an error occurs.

This script is this all it does.

song1.mp3
song2.mp3
etc...

When you move songs around, does the list that resides in request.py update and feed it to Liquidsoap to play in the new order?

song2.mp3
song1.mp3
etc...

I know how to do the scripting in ASP.NET and Classic ASP.
But I do not think they will work in this situation.

So, I am looking at how to script it in Python with SQL Server.
I can output a song per line.

Will that be all that is needed just to have that script inside of the request.py?
Just a file that is filled with songs that are being ordered by a database or other feed?

Thanks guys.

[vitoyucepi]

Hi @carrzkiss,
I don't remember exactly what I did in the code snippet, but it looks like I didn't explain some things.

def get_request()
  command = process.quote.command("python3", args=["request.py"])
  process = process.run(command)
  
  output = 
    if process.status == "exit" and process.status.code == 0 then
      process.stdout
    else
      null()
    end
  lines = null.map(fun(output) -> r/\r?\n/.split(output), output)
  uri = 
    try
      null.map(list.hd, lines)
    catch _ do
      null()
    end

  null.map(fun(uri) -> request.create(uri, temporary=true), uri)
end

This function creates a single request by extracting the first line from the script output.

[carrzkiss]

OK, so your script calls request.py and gets the FIRST line from that file every few seconds; it checks.
So, am I correct on what I need to write in my py script?
A list of songs and your script will then check and grab the song from.

[vitoyucepi]

I think it would be better to start a new discussion from scratch.

[carrzkiss]

New thread here 4359