Docker run image on Windows 11 gives error /bin/sh: 1: [: python3: unexpected operator

I have installed the following on my Windows 11 laptop:

• Python 3.10
• Pycharm editor
• WSL 2 from https://wslstorestorage.blob.core.windows.net/wslblob/wsl_update_x64.msi
• Latest Ubuntu from https://apps.microsoft.com/store/detail/ubuntu/9PDXGNCFSCZV?hl=nb-no&gl=no&rtc=1
• Docker desktop from https://desktop.docker.com/win/main/amd64/Docker%20Desktop%20Installer.exe

In Docker desktop I have enabled Kubernetes.

Now I have created a script in Python that I have called Books that is a API that gives a json with books:

main.py:

import flask
from flask import jsonify, request

app = flask.Flask(__name__) # Creates the Flask application object
app.config["DEBUG"] = True

# Create some test data for our catalog in the form of a list of dictionaries.
books = [
    {'id': 0,
     'title': 'A Fire Upon the Deep',
     'author': 'Vernor Vinge',
     'first_sentence': 'The coldsleep itself was dreamless.',
     'year_published': '1992'},
    {'id': 1,
     'title': 'The Ones Who Walk Away From Omelas',
     'author': 'Ursula K. Le Guin',
     'first_sentence': 'With a clamor of bells that set the swallows soaring, the Festival of Summer came to the city Omelas, bright-towered by the sea.',
     'published': '1973'},
    {'id': 2,
     'title': 'Dhalgren',
     'author': 'Samuel R. Delany',
     'first_sentence': 'to wound the autumnal city.',
     'published': '1975'}
]


@app.route('/', methods=['GET'])
def home():
    return '''<h1>Distant Reading Archive</h1>
<p>A prototype API for distant reading of science fiction novels.</p>'''


@app.route('/api/v1/resources/books/all', methods=['GET'])
def api_all():
    return jsonify(books)


@app.route('/api/v1/resources/books', methods=['GET'])
def api_id():
    # Check if an ID was provided as part of the URL.
    # If ID is provided, assign it to a variable.
    # If no ID is provided, display an error in the browser.
    if 'id' in request.args:
        id = int(request.args['id'])
    else:
        return "Error: No id field provided. Please specify an id."

    # Create an empty list for our results
    results = []

    # Loop through the data and match results that fit the requested ID.
    # IDs are unique, but other fields might return many results
    for book in books:
        if book['id'] == id:
            results.append(book)

    # Use the jsonify function from Flask to convert our list of
    # Python dictionaries to the JSON format.
    return jsonify(results)

app.run()

When I run the script from Pycharm everything works fine. I can view the API at http://127.0.0.1:5000/api/v1/resources/books/all

Now I try to build a docker image. I have created a file named dockerfile:

dockerfile:

# Specifying Python
FROM ubuntu:latest
RUN apt-get update -y
RUN apt-get install python3 -y
RUN apt-get install python3-pip -y
RUN pip install --upgrade pip

# Add Python script
ADD main.py main.py

# Install dependencies
# RUN pip install -r requirements.txt
RUN pip install flask

# Run script
CMD [ "python3" "./main.py" ]

I build the docker image with the following command, and it build OK:

docker build --tag books .

When I now open Powershell to run the docker image it gives me an error:

C:\Users\s>docker run books
/bin/sh: 1: [: python3: unexpected operator

>Solution :

You need a comma between commands in your Dockerfile. ie:

CMD ["python3", "./main.py"]

See CMD format here