Docker 容器不执行 Python 命令

Question

I have a simple script writecsv.py which queries an external API, parses the response, and writes to 2 CSVs.

My Dockerfile reads:

FROM python:3.8.5-slim-buster
COPY . /src
RUN pip install -r /src/requirements.txt
CMD ["python", "./src/writecsv.py"]

In the directory containing my Dockerfile, I have 4 files:

writecsv.py # My script that queries API and writes 2 csvs
keys.yaml # Stores my API keys which are read by writecsv.py
requirements.txt 
Dockerfile

When I build this image, I use docker build -t write-to-csv-application. and to run this image, I use docker run write-to-csv-application

I am able to show that the script runs, and the 2 CSV files are successfully created by printing the contents of the current working directory before and after calling csv.DictWriter.

So far, so good. Now I'd like to expose these files on localhost:5000, to be downloaded.

My current approach isn't working. I don't know Docker very well, so any suggestions are welcomed. Here's where things go wrong:

I then add 2 more lines to my Dockerfile; expose 5000, and http.server to get:

FROM python:3.8.5-slim-buster
COPY . /src
RUN pip install -r /src/requirements.txt
EXPOSE 5000/tcp
CMD ["python", "./src/writecsv.py"]
CMD python -m http.server -dp ./src/ 5000

Now when I build this image, again using docker build -t write-to-csv-application. and run this image using docker run -p 5000:5000 write-to-csv-application I don't get any command line output from the writecsv.py program, that I did previously. I am able to access localhost:5000 and see the image file structure, but I find that the files weren't created. The output in command line hangs indefinitely (which I would expect, as I don't have anything to terminate the http server.)

What I've tried:

• I wrote the files to./src/data/ and pointed the http.server to /src/data/, which doesn't exist.
• I pointed the http.server to./ and checked the entire file structure: they aren't being written anywhere when ran with docker run -p 5000:5000 write-to-csv-application

Answer 1

This worked for me. I neglected the requirements.txt. I just made a very basic example.

"The main purpose of a CMD is to provide defaults for an executing container". See the official docs for more information.

writecsv.py:

import csv 
    
fields = ['Name', 'Branch', 'Year', 'CGPA'] 
    
rows = [ ['Nikhil', 'COE', '2', '9.0'], 
         ['Sanchit', 'COE', '2', '9.1'], 
         ['Aditya', 'IT', '2', '9.3'], 
         ['Sagar', 'SE', '1', '9.5'], 
         ['Prateek', 'MCE', '3', '7.8'], 
         ['Sahil', 'EP', '2', '9.1']] 
    
filename = "university_records.csv"
    
with open(filename, 'w') as csvfile: 
    csvwriter = csv.writer(csvfile) 
    csvwriter.writerow(fields) 
    csvwriter.writerows(rows)

Dockerfile:

FROM python:3.8.5-slim-buster
WORKDIR /src
COPY . /src
EXPOSE 5000/tcp
RUN ["python", "./writecsv.py"]
CMD python -m http.server -d . 5000

docker build -t python-test . 
docker run --rm -it -p 5000:5000 --name python-test python-test