CODEWITHSUNDEEP
pythondocker
Aaditya R Krishnan
Aaditya R Krishnan

Reputation: 505

Python file writing is not working inside docker

I'm a trying to dockerize a python script in which file writing of a text file and CSV file is there. but it is not working, the file is not getting generated.

For reference my code is

FROM python:3



ADD ./HMS.py /
ADD ./constants.py /
ADD ./Docker.py /
ADD ./SNT.py /
ADD ./Utility.py /


RUN pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org docker
RUN pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org grepfunc
RUN pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org requests


CMD [ "python", "./HMS.py" ]

However, when I run the python script outside am able to generate the files. May I know why it is not getting generated inside the work directory.

UPDATE

    def write_log(self, filename, message, type='info'):
        with open(filename, 'a') as log:
            log.write('\n' + message)

    def write_csv(self, filepath, data):
        with open(filepath, 'a', newline='') as file:
            writer = csv.writer(file)
            writer.writerow(data)

constant file contain the path

LOG_FILE='./snt_alarm_log.txt'
COMPONENT_NAME='SNT Alarm'
DB_FILE='./snt.csv'

Upvotes: 5

Views: 3390

Answers (2)

Nate Anderson
Nate Anderson

Reputation: 21034

I am on a Windows machine with a Git bash trying to follow this tutorial. When I run this command to execute a Python script to write a file, I don't see the file in my local directory!

$ docker run --volume="/c/Users/nanders2/.python-xml-docker":/app pythonxml:latest

The issue is with Git Bash's Posix path conversion as described here.

This is due to Mingw/msys2 doing automatic path conversion; see http://www.mingw.org/wiki/Posix_path_conversion

You can disable this by prefixing paths with // or setting the MSYS_NO_PATHCONV=1 environment variable (see https://stackoverflow.com/a/34386471)

Because this path conversion happens before docker receives the value, its not something we can fix in docker.

The solution that works for me is to use double-forward-slash in my path

$ docker run --volume="//c//Users//nanders2//.python-xml-docker":/app pythonxml:latest

Or I could use Powershell (i.e. stop using Git Bash) instead, but I don't like that solution.

Slightly better solution is to use Docker Desktop itself to run the container, and manually specify the volume/mount arguments. screenshot of Docker Desktop, go to the Images tab and click "Run" on an image to set the volume/mount options manually

I started realizing the docker + Git Bash was struggling when it logged errors like this:

docker: Error response from daemon: the working directory 'C:/Program Files/Git/app' is invalid, it needs to be an absolute path.

Upvotes: 0

prithajnath
prithajnath

Reputation: 2115

Containers are ephemeral by nature. If you want to retain files generated inside a container you need to mount your host file system to the file system of the container. There are many ways to mount a volume, but a common way is a bind mount

docker run -v /path/to/host:/project sntalarmdocker_snt

Whatever gets saved to /project will be visible in /path/to/host even after the container is killed

Upvotes: 5

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