Environment variable behaviour in python

Question

I'm trying to access railway environment variables during the build process using python.Some of the python requirements use API keys for access that are under the GITHUB_TOKEN variable.My attempted workaround for not having the API keys in the requirements file, it generates a requirements.txt with python during the Docker build process.However, when accessing the environment variables in generate_requirements.py, it doesn't output any of the railway service variables.Is there any way of accessing these variables during the build process?Thanks in advance.The docker file looks like this:FROM python:3.13-slim

ENV DOCKER_ENV=1

RUN mkdir -p /app
WORKDIR /app

# Install system dependencies for Python and Django
RUN apt-get update 
RUN apt-get install -y --no-install-recommends git build-essential libpq-dev curl
RUN rm -rf /var/lib/apt/lists/*

# Install Node.js and Sass
RUN curl -fsSL https://deb.nodesource.com/setup_18.x | bash -
RUN apt-get install -y nodejs
RUN npm install -g sass

# Copy project files
COPY . .

# Install pip and other dependencies
RUN python -m ensurepip && python -m pip install --upgrade pip setuptools wheel
RUN pip install python-dotenv

# Generate requirements using API keys
RUN python generate_requirements.py

RUN pip install -r requirements.txt

# Compile SCSS to CSS
RUN sass /app/financemgmt/static/scss/build.scss:/financemgmt/static/css/build.css

EXPOSE 8000
CMD ["gunicorn", "--bind", "0.0.0.0:8000", "main.wsgi"]And the start of the generate_requirements.py file looks like this:import os
import subprocess
from dotenv import load_dotenv

load_dotenv()

for key, value in os.environ.items():
    print(f"{key}={value}")
    
github_token = os.environ.get("GITHUB_TOKEN")
   
if not github_token:
    raise ValueError("GITHUB_TOKEN not found in .env file")