Docker tutorial issues

Docker Desktop for Mac
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3

@denisroy
I mean its exactly the same as the tutorial.
docker-compose.yml

 iversion: "3"
 services:
   web:
     image: mjwrazor/repository:4
     deploy:
      replicas: 5
      resources:
        limits:
          cpus: "0.1"
          memory: 50M
      restart_policy:
        condition: on-failure
    ports:
      - "80:80"
    networks:
      - webnet
networks:
  webnet:

Dockerfile

`# Use an official Python runtime as a base image
FROM python:2.7-slim

# Set the working directory to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
ADD . /app

# Install any needed packages specified in requirements.txt
RUN pip install -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World

# Run app.py when the container launches
CMD ["python", "app.py"]`

There is no extension on the Dockerfile right?
I ran the commands in exact sequence given in the tutorial. I went back to do it again. When I make changes do I need to bump the tag an push every time? Or can I just make changes and only create a new tag when I want to? app.py is exact copy of the tutorial code.

When I try docker swarm init after restarting I get

Error response from daemon: This node is already part of a swarm. Use "docker swarm l join another one.