Serve a react app.

serve.py

import os
from flask import Flask, render_template, send_from_directory
app = Flask(__name__, static_folder="/app", template_folder="/app")


# Serve React App
@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def serve(path):
    print(path)
    if path != "" and os.path.exists(app.static_folder + '/' + path):
        return send_from_directory(app.static_folder, path)
    else:
        return send_from_directory(app.static_folder, 'index.html')

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

app.debug=True
app.run(host='0.0.0.0', port=80)
# app.run(port=80)