How to pack up a Python script in the form a Dockerfile

Question

I have a simple Python script with this header

from flask import Flask
app = Flask(__name__)

@app.route('/')
import os
import pandas as pd
from statsmodels.formula.api import ols
import statsmodels.api as sm

I have installed GitHub Desktop, Docker Desktop

I have created a folder in that I have

(.venv) (base) angel@Angels-MacBook-Pro docker % ls
Dockerfile      app.py          compose.yaml        requirements.txt

In requirements.txt I have

(.venv) (base) angel@Angels-MacBook-Pro docker % cat requirements.txt 
blinker==1.6.2
click==8.1.6
colorama==0.4.6
Flask==2.3.2
itsdangerous==2.1.2
Jinja2==3.1.2
MarkupSafe==2.1.3
Werkzeug==2.3.6
gunicorn==21.2.0

This is the commands I have run so far

docker init

Then this one returns error

(.venv) (base) angel@Angels-MacBook-Pro docker % docker compose up --build                         
[+] Building 3.9s (14/14) FINISHED                                                                                   docker:desktop-linux
 => [server internal] load .dockerignore                                                                                             0.1s
 => => transferring context: 680B                                                                                                    0.1s
 => [server internal] load build definition from Dockerfile                                                                          0.1s
 => => transferring dockerfile: 1.63kB                                                                                               0.1s
 => [server] resolve image config for docker.io/docker/dockerfile:1                                                                  2.3s
 => [server auth] docker/dockerfile:pull token for registry-1.docker.io                                                              0.0s
 => CACHED [server] docker-image://docker.io/docker/dockerfile:1@sha256:ac85f380a63b13dfcefa89046420e1781752bab202122f8f50032edf31b  0.0s
 => [server internal] load metadata for docker.io/library/python:3.9.12-slim                                                         1.3s
 => [server auth] library/python:pull token for registry-1.docker.io                                                                 0.0s
 => [server base 1/5] FROM docker.io/library/python:3.9.12-slim@sha256:364ada4cb4f943b603d330cbb3d26f689c8b54de51cb12bad1202de7dba3  0.0s
 => [server internal] load build context                                                                                             0.0s
 => => transferring context: 1.39kB                                                                                                  0.0s
 => CACHED [server base 2/5] WORKDIR /app                                                                                            0.0s
 => CACHED [server base 3/5] RUN adduser     --disabled-password     --gecos ""     --home "/nonexistent"     --shell "/sbin/nologi  0.0s
 => CACHED [server base 4/5] RUN --mount=type=cache,target=/root/.cache/pip     --mount=type=bind,source=requirements.txt,target=re  0.0s
 => [server base 5/5] COPY . .                                                                                                       0.0s
 => [server] exporting to image                                                                                                      0.0s
 => => exporting layers                                                                                                              0.0s
 => => writing image sha256:c207ecf929eb3dc4f172db22e56a19e7b89892fcdc31da80501cb3524e137f9d                                         0.0s
 => => naming to docker.io/library/docker-server                                                                                     0.0s
[+] Running 1/1
 ✔ Container docker-server-1  Recreated                                                                                              0.1s 
Attaching to docker-server-1
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [INFO] Starting gunicorn 21.2.0
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [INFO] Listening at: http://0.0.0.0:8000 (8)
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [INFO] Using worker: sync
docker-server-1  | [2023-09-22 11:09:20 +0000] [9] [INFO] Booting worker with pid: 9
docker-server-1  | [2023-09-22 11:09:20 +0000] [9] [ERROR] Exception in worker process
docker-server-1  | Traceback (most recent call last):
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/arbiter.py", line 609, in spawn_worker
docker-server-1  |     worker.init_process()
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/workers/base.py", line 134, in init_process
docker-server-1  |     self.load_wsgi()
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/workers/base.py", line 146, in load_wsgi
docker-server-1  |     self.wsgi = self.app.wsgi()
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/app/base.py", line 67, in wsgi
docker-server-1  |     self.callable = self.load()
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/app/wsgiapp.py", line 58, in load
docker-server-1  |     return self.load_wsgiapp()
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/app/wsgiapp.py", line 48, in load_wsgiapp
docker-server-1  |     return util.import_app(self.app_uri)
docker-server-1  |   File "/usr/local/lib/python3.9/site-packages/gunicorn/util.py", line 371, in import_app
docker-server-1  |     mod = importlib.import_module(module)
docker-server-1  |   File "/usr/local/lib/python3.9/importlib/__init__.py", line 122, in import_module
docker-server-1  |     raise TypeError(msg.format(name))
docker-server-1  | TypeError: the 'package' argument is required to perform a relative import for '.venv.lib.python3.9.site-packages.eventlet.wsgi'
docker-server-1  | [2023-09-22 11:09:20 +0000] [9] [INFO] Worker exiting (pid: 9)
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [ERROR] Worker (pid:9) exited with code 3
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [ERROR] Shutting down: Master
docker-server-1  | [2023-09-22 11:09:20 +0000] [8] [ERROR] Reason: Worker failed to boot.
docker-server-1 exited with code 3

yaml

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Docker compose reference guide at
# https://docs.docker.com/compose/compose-file/

# Here the instructions define your application as a service called "server".
# This service is built from the Dockerfile in the current directory.
# You can add other services your application may depend on here, such as a
# database or a cache. For examples, see the Awesome Compose repository:
# https://github.com/docker/awesome-compose
services:
  server:
    build:
      context: .
    ports:
      - 8000:8000

# The commented out section below is an example of how to define a PostgreSQL
# database that your application can use. `depends_on` tells Docker Compose to
# start the database before your application. The `db-data` volume persists the
# database data between container restarts. The `db-password` secret is used
# to set the database password. You must create `db/password.txt` and add
# a password of your choosing to it before running `docker compose up`.
#     depends_on:
#       db:
#         condition: service_healthy
#   db:
#     image: postgres
#     restart: always
#     user: postgres
#     secrets:
#       - db-password
#     volumes:
#       - db-data:/var/lib/postgresql/data
#     environment:
#       - POSTGRES_DB=example
#       - POSTGRES_PASSWORD_FILE=/run/secrets/db-password
#     expose:
#       - 5432
#     healthcheck:
#       test: [ "CMD", "pg_isready" ]
#       interval: 10s
#       timeout: 5s
#       retries: 5
# volumes:
#   db-data:
# secrets:
#   db-password:
#     file: db/password.txt

Dockerfile

FROM python:3.9
WORKDIR /docker
COPY . /docker
RUN pip install -r requirements.txt
CMD ["python", "./app.py"]

Answer 1

Not sure which tutorial you're following, but I think it's overly complicated. You do not need the compose file, and the Dockerfile has some issues:

First, specify what you want to copy into the container. That is requirements.txt and app.py. Then also, tell pip where the requirements file is. This works in terms of putting a container together. I am not testing the python script itself, this is on you.

$ cat Dockerfile
FROM python:3.9
WORKDIR /docker
COPY ["app.py", "requirements.txt" ,"/docker/"]
RUN pip install -r /docker/requirements.txt
CMD ["python", "./app.py"]

$ cat app.py
from flask import Flask
app = Flask(__name__)

@app.route('/')
import os
import pandas as pd
from statsmodels.formula.api import ols
import statsmodels.api as sm

$ cat requirements.txt
blinker==1.6.2
click==8.1.6
colorama==0.4.6
Flask==2.3.2
itsdangerous==2.1.2
Jinja2==3.1.2
MarkupSafe==2.1.3
Werkzeug==2.3.6
gunicorn==21.2.0

$ docker build -t atpoint/foo:1.0 .
[+] Building 5.8s (9/9) FINISHED
 => [internal] load build definition from Dockerfile                                                                                                                                                                                                                                       0.0s
 => => transferring dockerfile: 38B                                                                                                                                                                                                                                                        0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                                                          0.0s
 => => transferring context: 2B                                                                                                                                                                                                                                                            0.0s
 => [internal] load metadata for docker.io/library/python:3.9                                                                                                                                                                                                                              5.7s
 => [1/4] FROM docker.io/library/python:3.9@sha256:031b2a713079b2436e6c2102dbffbce109c9c2582ad0867c380e3c8d7fed477f                                                                                                                                                                        0.0s
 => [internal] load build context                                                                                                                                                                                                                                                          0.0s
 => => transferring context: 64B                                                                                                                                                                                                                                                           0.0s
 => CACHED [2/4] WORKDIR /docker                                                                                                                                                                                                                                                           0.0s
 => CACHED [3/4] COPY [app.py, requirements.txt ,/docker/]                                                                                                                                                                                                                                 0.0s
 => CACHED [4/4] RUN pip install -r /docker/requirements.txt                                                                                                                                                                                                                               0.0s
 => exporting to image                                                                                                                                                                                                                                                                     0.0s
 => => exporting layers                                                                                                                                                                                                                                                                    0.0s
 => => writing image sha256:6a6f1b08c8343608d2eacaa8463a1638491b504a3230ab00d45a7b32a41e1a43                                                                                                                                                                                               0.0s
 => => naming to docker.io/atpoint/foo:1.0                                                                                                                                                                                                                                                 0.0s

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them

Your container is now available as atpoint/foo:1.0 which reads as username (atpoint), name of container (foo) and a version number / tag (1.0), all of which is free to choose. This is the most basic way of packing a container.