app.py

from flask import Flask
from sqlalchemy import SQLAlchemy

db = SQLAlchemy()

def create_app(info=None):
    app = Flask(__name__)
    # config app commented out
    db.init_app(app)
    
    import posts
    
    app.register_blueprint(posts.bp, url_prefix='/')
    
    return app

posts.__init__.py

from flask import Blueprint

bp = Blueprint('posts', __name__)

@bp.record_once
def register(state):
    from posts import views

posts.views.py

from flask import render_template
from posts import bp

@bp.route('/')
def show_posts():
    return render_template('show_posts.html')

@bp.route('/add')
def add_posts():
    return render_template('add_posts.html')