Added Python example.

Author: lucacillario

.gitignore

@@ -1,4 +1,6 @@
 node_modules/
+venv/
+env/
 .DS_Store
 .idea
 *.tmp

index.js renamed to nodejs/index.js

@@ -0,0 +1,70 @@
+import logging
+import os
+
+import redis
+
+LOGGING_LEVEL = os.environ.get("LOGLEVEL", "INFO")
+logging.basicConfig(
+    format="[%(asctime)s] %(levelname)-8s %(message)s",
+    level=LOGGING_LEVEL,
+)
+
+REDIS_URL = os.environ.get("REDIS_URL", "redis://localhost:6379")
+SUB_KEY = "__keyspace@0__:tokens:*"
+
+# pub/sub clients do not allow the execution of non-pubsub commands
+# so, we're using a dedicated client for subscribing to keyspace events
+# and a dedicated client for non-pubsub commands, needed to handle the scoreboard logic
+sub_client = redis.Redis.from_url(REDIS_URL, decode_responses=True).pubsub()
+client = redis.Redis.from_url(REDIS_URL, decode_responses=True)
+
+
+def keyspace_event_handler(event):
+    """Handles the keyspace events.
+
+    This is an example of the event format:
+    {
+        'type': 'pmessage',
+        'pattern': '__keyspace@0__:tokens:*',
+        'channel': '__keyspace@0__:tokens:luca',
+        'data': 'sadd'
+    }
+    """
+    logging.debug(f"Received new event: {event}")
+    event_type = event['data']
+    channel = event["channel"]
+    logging.info(f"event >>> {event_type} on {channel}")
+    affected_key = channel.split(":", maxsplit=1)[1]
+    how_many = client.scard(affected_key)
+    logging.info(f"Set cardinality {affected_key} is {how_many}")
+
+    username = affected_key.split(":")[1]
+
+    if how_many > 0:
+        client.zadd("scoreboard", {username: how_many})
+    else:
+        client.zrem("scoreboard", username)
+
+    scoreboard = client.zrange("scoreboard", 0, -1, desc=True, withscores=True)
+    logging.info(f"Scores: {scoreboard}")
+
+
+def main():
+    sub_client.psubscribe(**{SUB_KEY: keyspace_event_handler})
+    pubsub_worker_thread = None
+    try:
+        logging.debug("Waiting for events...")
+        pubsub_worker_thread = sub_client.run_in_thread(sleep_time=.01)
+        pubsub_worker_thread.join()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        # gracefully stops the clients, for example when receives a `KeyboardInterrupt` (e.g. CTRL + c)
+        logging.debug("Stopping the application...")
+        if pubsub_worker_thread:
+            pubsub_worker_thread.stop()
+        client.close()
+
+
+if __name__ == "__main__":
+    main()

package-lock.json renamed to nodejs/package-lock.json

@@ -0,0 +1,6 @@
+async-timeout==4.0.2
+Deprecated==1.2.13
+packaging==21.3
+pyparsing==3.0.9
+redis==4.3.4
+wrapt==1.14.1