maybe.py

import praw, time, requests, json

r = praw.Reddit(
    client_id="",
    client_secret="",
    username="",
    password="",
    user_agent="script:some_random_identifier:v1.0 (by /u/you)")

sub = r.subreddit("your_sub") # no /r/ here

while True:
  
  with open('path/to/data.json') as data_file:    
    data = json.load(data_file)

  sidebar_template = sub.wiki["sidebar_template"].content_md
  sidebar = sidebar_template.replace("{NUM}", data["USERS_ONLINE"])

  edit_msg = "https://github.com/{}/compare/{}"
  sub.wiki["config/sidebar"].edit(sidebar, edit_msg)

  time.sleep(60 * 5) # in seconds, this sets it to 5 minutes