关于Flask-login你需要知道的：此扩展与应用程序的用户模型一起工作，并期望在其中实现某些属性和方法。（源代码：https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-v-user-logins）。
以下列出了四个必需项目：

• is_authenticated：如果用户具有有效凭据，则为True，否则为False的属性。
• is_active：如果用户的帐户处于活动状态，则为True，否则为False。
• is_anonymous：对于普通用户为False，对于特殊匿名用户为True的属性。
• get_id()：以字符串形式返回用户的唯一标识符的方法

不幸的是，官方文档和Miguel Grinberg的优秀博客中的所有示例都使用SQLAlchemy。好消息是，可以使用Pymongo实现它...

解决方案

1. routes.py

from flask import Flask
from flask_pymongo import PyMongo
from flask_login import LoginManager
from flask import render_template, url_for, request, flash
from app.forms import Login
from flask import request
from werkzeug.urls import url_parse
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import current_user, login_user, logout_user, login_required

mongo = PyMongo(app)
login = LoginManager(app)
login.login_view = 'login'

class User:
    def __init__(self, username):
        self.username = username

    @staticmethod
    def is_authenticated():
        return True

    @staticmethod
    def is_active():
        return True

    @staticmethod
    def is_anonymous():
        return False

    def get_id(self):
        return self.username

    @staticmethod
    def check_password(password_hash, password):
        return check_password_hash(password_hash, password)

    @login.user_loader
    def load_user(username):
        u = mongo.db.Users.find_one({"Name": username})
        if not u:
            return None
        return User(username=u['Name'])

    @app.route('/login', methods=['GET', 'POST'])
    def login():
        if current_user.is_authenticated:
            return redirect(url_for('index'))
        form = Login()
        if form.validate_on_submit():
            user = mongo.db.Users.find_one({"Name": form.name.data})
            if user and User.check_password(user['Password'], form.password.data):
                user_obj = User(username=user['Name'])
                login_user(user_obj)
                next_page = request.args.get('next')
                if not next_page or url_parse(next_page).netloc != '':
                    next_page = url_for('index')
                return redirect(next_page)
            else:
                flash("Invalid username or password")
        return render_template('login.html', title='Sign In', form=form)

    @app.route('/logout')
    def logout():
        logout_user()
        return redirect(url_for('login'))

1. form.py

from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField, PasswordField
from wtforms.validators import DataRequired

class Login(FlaskForm):
    name = StringField('name' validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    login = SubmitField('Login')

假设我们在Mongodb端有一个集合（Users），其中包含一些登录信息。例如：

{
  Name: [username],
  Password: [hashed_password]
}

要进一步解释每行代码的作用，我建议您参考以下链接：

• https://boh717.github.io/post/flask-login-and-mongodb/
• https://flask-login.readthedocs.io/en/latest/

我发现下面的作品与flask-login，UserMixin，pymongo
这里是用户模型

import datetime
import uuid
from depo import bcrypt, login_manager
from flask import session, flash
from depo.common.database import Database
from depo.models.blog import Blog
from flask_login import UserMixin

class User(UserMixin):

    def __init__(self, username, email, password, _id=None):

        self.username = username
        self.email = email
        self.password = password
        self._id = uuid.uuid4().hex if _id is None else _id

    def is_authenticated(self):
        return True
    def is_active(self):
        return True
    def is_anonymous(self):
        return False
    def get_id(self):
        return self._id

    @classmethod
    def get_by_username(cls, username):
        data = Database.find_one("users", {"username": username})
        if data is not None:
            return cls(**data)

    @classmethod
    def get_by_email(cls, email):
        data = Database.find_one("users", {"email": email})
        if data is not None:
            return cls(**data)

    @classmethod
    def get_by_id(cls, _id):
        data = Database.find_one("users", {"_id": _id})
        if data is not None:
            return cls(**data)

    @staticmethod
    def login_valid(email, password):
        verify_user = User.get_by_email(email)
        if verify_user is not None:
            return bcrypt.check_password_hash(verify_user.password, password)
        return False

    @classmethod
    def register(cls, username, email, password):
        user = cls.get_by_email(email)
        if user is None:
            new_user = cls( username, email, password)
            new_user.save_to_mongo()
            session['email'] = email
            return True
        else:
            return False

    def json(self):
        return {
            "username": self.username,
            "email": self.email,
            "_id": self._id,
            "password": self.password
        }

    def save_to_mongo(self):
        Database.insert("users", self.json())

这里是路线

from flask import flash, render_template, request, session, make_response,  redirect, url_for
from depo import app, bcrypt, login_manager
from depo.models.blog import Blog
from depo.models.post import Post
from depo.models.user import User
from depo.common.database import Database
from depo.usercon.forms import RegistrationForm, LoginForm
from flask_login import login_user

@app.before_first_request
def initialize_database():
    Database.initialize()

@app.route("/register", methods=['GET', 'POST'])
def register():
    form = RegistrationForm()
    if form.validate_on_submit():

        if request.method == 'POST':
            username = request.form["username"]
            email = request.form["email"]
            password = bcrypt.generate_password_hash(request.form["password"])
                       .decode('utf-8')
            find_user =  User.get_by_email(email)
            if find_user is None:
                User.register(username, email, password)
                flash(f'Account created for {form.username.data}!', 'success')
                return redirect(url_for('home'))
            else:
                flash(f'Account already exists for {form.username.data}!', 'success')
    return render_template('register.html', title='Register', form=form)
@app.route("/login", methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        email = request.form["email"]
        password = request.form["password"]
        find_user = Database.find_one("users", {"email": email})
        if User.login_valid(email, password):
            loguser = User(find_user["_id"], find_user["email"], find_user["password"])
            login_user(loguser, remember=form.remember.data)
            flash('You have been logged in!', 'success')
            return redirect(url_for('home'))
        else:
            flash('Login Unsuccessful. Please check email and password', 'danger')
    return render_template('login.html', title='Login', form=form)

@login_manager.user_loader
def load_user(user_id):
    user =User.get_by_id(user_id)
    if user is not None:
        return User(user["_id"])
    else:
        return None

如果尚未初始化，可能还需要app的一些代码

from flask_login import LoginManager
login_manager = LoginManager(app)

我遇到了同样的问题，https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-v-user-logins。
我做了一些修改，让它在Mongo中运行，但我确实从MongoClient切换到了MongoEngine。

__init__.py

from flask import Flask
from config import Config
from flask_mongoengine import MongoEngine, Document
from flask_login import LoginManager

app = Flask(__name__)
app.config.from_object(Config)

login = LoginManager(app)
login.login_view = 'login'

db = MongoEngine(app)

from app import routes
from app.model import user

.

app/model/user.py

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

@login.user_loader
def load_user(id):
    return User.objects.get(id=id)

class User(UserMixin, db.Document):
    meta = {'collection': 'users'}
    username = db.StringField(default=True)
    email = db.EmailField(unique=True)
    password_hash = db.StringField(default=True)
    active = db.BooleanField(default=True)
    isAdmin = db.BooleanField(default=False)
    timestamp = db.DateTimeField(default=datetime.now())

    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)

.

app/forms.py

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, BooleanField, SubmitField
from wtforms.validators import ValidationError, DataRequired, Email, EqualTo
from app.model.user import User

class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    remember_me = BooleanField('Remember Me')
    submit = SubmitField('Sign In')

class RegistrationForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])
    password2 = PasswordField(
        'Repeat Password', validators=[DataRequired(), EqualTo('password')])
    submit = SubmitField('Register')

    def validate_username(self, username):
        user = User.objects(username=username.data).first()
        if user is not None:
            raise ValidationError('Please use a different username.')

    def validate_email(self, email):
        user = User.objects(email=email.data).first()
        if user is not None:
            raise ValidationError('Please use a different email address.')

.

app/routes.py

from flask import render_template, flash, redirect, request, url_for
from app import app, db
from app.forms import LoginForm, RegistrationForm
from flask_login import current_user, login_user, login_required, logout_user
from app.model.user import User

@app.route('/')
@app.route('/index')
@login_required
def index():
    posts = [
        {
            'author': {'username': 'John'},
            'body': 'Beautiful day in Portland!'
        },
        {
            'author': {'username': 'Susan'},
            'body': 'The Avengers movie was so cool!'
        }
    ]
    return render_template("index.html", title='Home Page', posts=posts)

@app.route('/login', methods=['GET', 'POST'])
def login():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = LoginForm()
    if form.validate_on_submit():
        user = User.objects(username=form.username.data).first()
        if user is None or not user.check_password(form.password.data):
            flash('Invalid username or password')
            return redirect(url_for('login'))
        login_user(user, remember=form.remember_me.data)
        next_page = request.args.get('next')
        if not next_page or url_parse(next_page).netloc != '':
            next_page = url_for('index')
        return redirect(next_page)
    return render_template('login.html', title='Sign In', form=form)

@app.route('/logout')
@login_required
def logout():
    logout_user()
    return redirect(url_for('index'))

@app.route('/register', methods=['GET', 'POST'])
def register():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = RegistrationForm()
    if form.validate_on_submit():
        user = User(username=form.username.data, email=form.email.data)
        user.set_password(form.password.data)
        user.save()
        flash('Congratulations, you are now a registered user!')
        return redirect(url_for('login'))
    return render_template('register.html', title='Register', form=form)

关于Sazzad
在Flask文档中：

def get_id(self):
    try:
        return str(self.id)
    except AttributeError:
        raise NotImplementedError("No `id` attribute - override `get_id`") from None

所以，不是“_id”就是“id”