Create a file "Dockerfile" with below content

FROM python:3.7
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
ENTRYPOINT [ "python" ]
CMD [ "main.py" ]

Create a "Procfile" with following content

web: gunicorn main:app

create a file ".circleci\config.yml" with following content

version: 2.1
orbs:
  heroku: circleci/heroku@1.0.1
jobs:
  build-and-test:
    executor: heroku/default
    docker:
      - image: circleci/python:3.6.2-stretch-browsers
        auth:
          username: mydockerhub-user
          password: $DOCKERHUB_PASSWORD  # context / project UI env-var reference
    steps:
      - checkout
      - restore_cache:
          key: deps1-{{ .Branch }}-{{ checksum "requirements.txt" }}
      - run:
          name: Install Python deps in a venv
          command: |
            echo 'export TAG=0.1.${CIRCLE_BUILD_NUM}' >> $BASH_ENV
            echo 'export IMAGE_NAME=python-circleci-docker' >> $BASH_ENV
            python3 -m venv venv
            . venv/bin/activate
            pip install --upgrade pip
            pip install -r requirements.txt
      - save_cache:
          key: deps1-{{ .Branch }}-{{ checksum "requirements.txt" }}
          paths:
            - "venv"
      - run:
          command: |
            . venv/bin/activate
            python -m pytest -v tests/test_script.py
      - store_artifacts:
          path: test-reports/
          destination: tr1
      - store_test_results:
          path: test-reports/
      - setup_remote_docker:
          version: 19.03.13
      - run:
          name: Build and push Docker image
          command: |
            docker build -t $DOCKERHUB_USER/$IMAGE_NAME:$TAG .
            docker login -u $DOCKERHUB_USER -p $DOCKER_HUB_PASSWORD_USER docker.io
            docker push $DOCKERHUB_USER/$IMAGE_NAME:$TAG
  deploy:
    executor: heroku/default
    steps:
      - checkout
      - run:
          name: Storing previous commit
          command: |
            git rev-parse HEAD > ./commit.txt
      - heroku/install
      - setup_remote_docker:
          version: 18.06.0-ce
      - run:
          name: Pushing to heroku registry
          command: |
            heroku container:login
            #heroku ps:scale web=1 -a $HEROKU_APP_NAME
            heroku container:push web -a $HEROKU_APP_NAME
            heroku container:release web -a $HEROKU_APP_NAME

workflows:
  build-test-deploy:
    jobs:
      - build-and-test
      - deploy:
          requires:
            - build-and-test
          filters:
            branches:
              only:
                - main

to create requirements.txt

pip freeze>requirements.txt

initialize git repo

git init
git add .
git commit -m "first commit"
git branch -M main
git remote add origin <github_url>
git push -u origin main

create a account at circle ci

Circle CI

setup your project

Setup project

Select project setting in CircleCI and below environment variable

DOCKERHUB_USER
DOCKER_HUB_PASSWORD_USER
HEROKU_API_KEY
HEROKU_APP_NAME
HEROKU_EMAIL_ADDRESS
DOCKER_IMAGE_NAME=wafercircle3270303

to update the modification

git add .
git commit -m "proper message"
git push