Blueprint

Split up your app routes into separate files and register them at like /api/v1

Creation

simplepage.py

from flask import Blueprint

simple_page = Blueprint('simple_page', __name__,
                        template_folder='templates') #can leave template_folders out

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

Registering

app.py

from yourapplication.simple_page import simple_page

app = Flask(__name__)
app.register_blueprint(simple_page)

app.register_blueprint(user, url_prefix='/user')

Linking

url_for('admin.index')