Question 83437 in Docker Question posted in
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Container not writing data to physical disk file – Docker

Python Code:

import datetime,os
data = ""
with open("D://PythonService//Test.txt", "w") as outFile:
    outFile.write(data + "Service started at - {}n".format(datetime.datetime.now()))
    outFile.close()

Dockerfile

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

docker-compose.yml

version: '3.4'
services:
    newfoldercopy:
        image: newfoldercopy
        build:
          context: .
          dockerfile: ./Dockerfile
        volumes:
          - D:/PythonService:/var/lib/data/

I am trying to mount my physical file system path to the container.
But the container is not writing data on a physical file, the container is writing data on a container virtual file.

Tags:

3

Answers


  1. 0

    As I understand

    D:/PythonService – local path

    /var/lib/data/ – path inside container

    In Python code you should use container path (/var/lib/data/) not local path (D:/PythonService)

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  2. 0

    Your code should be something like with open("/var/lib/data/Test.txt", "w") as outFile:

    all files written at /var/lib/data folder inside the container will be available to D:/PythonService

    volumes:
  - <host directory>:<container directory>
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  3. 0

    Change:

    with open("D://PythonService//Test.txt", "w") as outFile:

    to:

    with open("/var/lib/data/Test.txt", "w") as outFile:

    because of this line in your docker-compose.yml:

            volumes:
          - D:/PythonService:/var/lib/data/

    Also instead of:

    outFile.write(data + "Service started at - {}n".format(datetime.datetime.now()))

    You can use f-string:

    outFile.write(f'{data} Service started at - {datetime.datetime.now()}n')

    which makes your code more readable.

    Also as I understood, using with open() closes your file automatically, so you can change your Python code from:

    with open("D://PythonService//Test.txt", "w") as outFile:
    outFile.write(data + "Service started at - {}n".format(datetime.datetime.now()))
    outFile.close()

    to:

    with open("/var/lib/data/Test.txt", "w") as outFile:
    outFile.write(f'{data} Service started at - {datetime.datetime.now()}n')
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