阐明如何在 Docker 中指定来自 Python 的文件路径

Question

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: /backend\data\distanceMatrixv2.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 .

Answer 1

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, ie 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 .

Answer 2

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"