models.py

from app import db
from datetime import datetime
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import UserMixin
from app import login

@login.user_loader
def load_user(id):
    return User.query.get(int(id))

followers = db.Table(
    'followers',
    db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('followed_id', db.Integer, db.ForeignKey('user.id'))
)

class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(120), index=True, unique=True)
    password_hash = db.Column(db.String(128))
    last_seen = db.Column(db.DateTime, default=datetime.utcnow)
    about = db.Column(db.String(200))
    post = db.relationship("Post", backref='author', lazy="dynamic")
    followed = db.relationship(
        'User', secondary=followers,
        primaryjoin=(followers.c.follower_id == id),
        secondaryjoin=(followers.c.followed_id == id),
        backref=db.backref('followers', lazy='dynamic'), lazy='dynamic')
    def __repr__(self):
        return "<User {}>".format(self.username)
    def set_password(self, password):
        self.password_hash=generate_password_hash(password)
    def check_password(self, password):
        return check_password_hash(self.password_hash, password)
    def avatar(self, size=128):
        return "https://api.dicebear.com/6.x/identicon/svg?seed={}&size={}".format(self.username, size)
    def follow(self, user):
        if not self.is_following(user):
            self.followed.append(user)

    def unfollow(self, user):
        if self.is_following(user):
            self.followed.remove(user)

    def is_following(self, user):
        return self.followed.filter(
            followers.c.followed_id == user.id).count() > 0

    def followed_posts(self):
        followed =  Post.query.join(
            followers, (followers.c.followed_id == Post.user_id)).filter(
            followers.c.follower_id == self.id)
        own = Post.query.filter_by(user_id=self.id)
        return followed.union(own).order_by(Post.timestamp.desc())

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    body = db.Column(db.String(500))
    timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
    user_id = db.Column(db.Integer, db.ForeignKey("user.id"))
    def __repr__(self):
        return "<Post {}>".format(self.body)