Flask项目引入flask-login时出现ImportError：无法导入url_decode

我在用Flask构建Web博客应用，引入flask-login库处理用户登录功能时，运行程序触发了ImportError。

项目目录结构 #

>flask_blog1
    >flaskblog
        >static
        >templates
        >__init__.py
        >forms.py
        >models.py
        >routes.py
    >instance
        >site.db
    >venv
    >requirements.txt
    >run.py

run.py代码 #

from flaskblog import app

if __name__ == "__main__":
    app.run(debug=True)

init.py代码 #

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_bcrypt import Bcrypt
from flask_login import LoginManager

app = Flask(__name__)
app.config["SECRET_KEY"] = "5791628bb0b13ce0c676dfde280ba245"
app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///site.db"
db = SQLAlchemy(app)
bcrypt = Bcrypt(app)
login_manager = LoginManager(app)

from flaskblog import routes

models.py代码 #

from datetime import datetime

# from .extensions import db
from flaskblog import db, login_manager
from flask_login import UserMixin


@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))


class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(20), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    image_file = db.Column(db.String(20), nullable=False, default="default.jpg")
    password = db.Column(db.String(60), nullable=False)
    posts = db.relationship("Post", backref="author", lazy=True)

    def __repr__(self):
        return f"User('{self.username}', '{self.email}', '{self.image_file}')"


class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100), nullable=False)
    date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    content = db.Column(db.Text, nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False)

    def __repr__(self):
        return f"Post('{self.title}', '{self.date_posted}')"

routes.py代码 #

from flask import render_template, flash, redirect, url_for
from flaskblog import app, db, bcrypt
from flaskblog.forms import RegistrationForm, LoginForm
from flaskblog.models import User, Post
from flask_login import login_user

posts = [
    {
        "author": "Ashutosh Chapagain",
        "title": "Blog Post 1",
        "content": "First Post Content",
        "date_posted": "October 1, 2023",
    },
    {
        "author": "Ash Dhakal",
        "title": "Blog Post 2",
        "content": "Second Post Content",
        "date_posted": "October 2, 2023",
    },
]


@app.route("/")
@app.route("/home")
def home():
    return render_template("home.html", posts=posts)


@app.route("/about")
def about():
    return render_template("about.html", title="About")


@app.route("/register", methods=["GET", "POST"])
def register():
    form = RegistrationForm()
    if form.validate_on_submit():
        hashed_password = bcrypt.generate_password_hash(form.password.data).decode(
            "utf-8"
        )
        user = User(
            username=form.username.data, email=form.email.data, password=hashed_password
        )
        db.session.add(user)
        db.session.commit()
        flash(f"Your account has been created! You are now able to log in!", "success")
        return redirect(url_for("login"))
    return render_template("register.html", title="Register", form=form)


@app.route("/login", methods=["GET", "POST"])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user and bcrypt.check_password_hash(user.password, form.password.data):
            login_user(user, remember=form.remember.data)
            return redirect(url_for("home"))
        else:
            flash("Login Unsuccessful. Please check email and password", "danger")
    return render_template("login.html", title="Login", form=form)

forms.py代码 #

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField, BooleanField
from wtforms.validators import DataRequired, Length, Email, EqualTo, ValidationError
from flaskblog.models import User


class RegistrationForm(FlaskForm):
    username = StringField(
        "Username", validators=[DataRequired(), Length(min=2, max=20)]
    )
    email = StringField("Email", validators=[DataRequired(), Email()])
    password = PasswordField("Password", validators=[DataRequired()])
    confirm_password = PasswordField(
        "Confirm Password", validators=[DataRequired(), EqualTo("password")]
    )
    submit = SubmitField("Sign Up")

    def validate_username(self, username):
        user = User.query.filter_by(username=username.data).first()
        if user:
            raise ValidationError(
                "That username is taken. Please choose a different one."
            )

    def validate_email(self, email):
        user = User.query.filter_by(email=email.data).first()
        if user:
            raise ValidationError("That email is taken. Please choose a different one.")


class LoginForm(FlaskForm):
    email = StringField("Email", validators=[DataRequired(), Email()])
    password = PasswordField("Password", validators=[DataRequired()])
    remember = BooleanField("Remember Me")
    submit = SubmitField("Login")

报错信息 #

(venv) asu@asu-Lenovo-Legion-5-15ARH05:/media/asu/Data/Projects/flask_blog1$ python3 run.py
Traceback (most recent call last):
  File "/media/asu/Data/Projects/flask_blog1/run.py", line 1, in <module>
    from flaskblog import app
  File "/media/asu/Data/Projects/flask_blog1/flaskblog/__init__.py", line 4, in <module>
    from flask_login import LoginManager
  File "/media/asu/Data/Projects/flask_blog1/venv/lib/python3.10/site-packages/flask_login/__init__.py", line 12, in <module>
    from .login_manager import LoginManager
  File "/media/asu/Data/Projects/flask_blog1/venv/lib/python3.10/site-packages/flask_login/login_manager.py", line 33, in <module>
    from .utils import _create_identifier
  File "/media/asu/Data/Projects/flask_blog1/venv/lib/python3.10/site-packages/flask_login/utils.py", line 14, in <module>
    from werkzeug.urls import url_decode
ImportError: cannot import name 'url_decode' from 'werkzeug.urls' (/media/asu/Data/Projects/flask_blog1/venv/lib/python3.10/site-packages/werkzeug/urls.py)

解决办法 #

这个错误是因为Werkzeug 2.3及以上版本移除了url_decode函数，而当前使用的flask-login版本未适配这个变更。有两种解决方式：

方式一：降低Werkzeug版本到兼容版本 #

在虚拟环境中执行以下命令，安装兼容的Werkzeug版本：

pip install werkzeug==2.2.3

方式二：升级Flask-Login到最新版本 #

新版本的Flask-Login已经适配了Werkzeug的API变化，执行升级命令即可：

pip install --upgrade flask-login

内容的提问来源于stack exchange，提问作者Ashutosh Chapagain