ruler_app.py

import os
from subprocess import call
from flask import Flask, render_template, send_from_directory

app = Flask(__name__)

app.route('/')
def index():
    return render_template('index.html')

app.route('/<int:length>')
def ruler(length):
    return send_from_directory(
        os.path.abspath(os.path.curdir),
        call(f'dxf-ruler-generator {length}'),
        as_attachment=True
    )