Question 82267 in Docker Question posted in
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Clarify how to specify file paths inside Docker coming from Python

I have created a Docker image with for a Flask app. Inside my Flask app, this is how I specify the file paths.

dPath = os.getcwd() + "\data\distanceMatrixv2.csv"

This should ideally resolve in a filepath similar to app/data/distanceMatrixv2.csv. This works when I do a py main.py run in the CMD. After making sure I am in the same directory, creating the image and running the Docker image via docker run -it -d -p 5000:5000 flaskapp, it throws me the error below when I try to do any processing.

FileNotFoundError: /backenddatadistanceMatrixv2.csv not found.

I believe this is due to how Docker resolves file paths but I am a bit lost on how to "fix" this. I am using Windows while my Docker image is built with FROM node:lts-alpine.

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2

Answers


  1. 0

    node:lts-alpine is based on Alpine which is a Linux distro. So your python program runs under Linux and should use Linux file paths, i.e. forward slashes like

    dPath = os.getcwd() + "/data/distanceMatrixv2.csv"

    It looks like os.getcwd() returns /backend. So the full path becomes /backend/data/distanceMatrixv2.csv.

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  2. 0

    The os.path library can do this portably across operating systems. If you write this as

    import os
import os.path

dPath = os.path.join(os.getcwd(), "data", "distanceMatrixv2.csv")

    it will work whether your (Windows) system uses DOS-style backslash-separated paths or your (Linux) system uses Unix-style forward slashes.

    Python 3.4 also added a pathlib library, if you prefer a more object-oriented approach. This redefines the Python / division operator to concatenate paths, using the native path separator. So you could also write

    from pathlib import Path

dPath = Path.cwd() / "data" / "distanceMatrixv2.csv"
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