SQLAlchemy“没有这样的表：用户”使用 Flask 进行用户注册时出错

Question

我第一次使用 Flask 和 SQLAlchemy 开发用户身份验证系统。当尝试注册用户时，我遇到以下错误：

ERROR in app: Exception on /register [POST]
Traceback (most recent call last):
  File "D:\anaconda\lib\site-packages\sqlalchemy\engine\base.py", line 1971, in _exec_context
    self.dialect.do_execute(
  File "D:\anaconda\lib\site-packages\sqlalchemy\engine\default.py", line 919, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such table: user

我正在尝试做的事情：

我正在尝试创建一个用户注册表单。提交表单后，用户的信息应保存到 SQLite 数据库中。

代码片段：

from flask import Flask, render_template, request, jsonify, url_for, redirect
from flask_sqlalchemy import SQLAlchemy
from flask_login import UserMixin, login_user, LoginManager, login_required, logout_user
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import InputRequired, Length, ValidationError
from flask_bcrypt import Bcrypt
import pytest


app = Flask(__name__)
bcrypt = Bcrypt(app)
db=SQLAlchemy()
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///database.db'
app.config['SECRET_KEY'] = 'thisisasecretkey'
db.init_app(app)

login_manager= LoginManager()
login_manager.init_app(app)
login_manager.login_view= "login"

@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), nullable=False)
    password=db.Column(db.String(80), nullable=False)

class RegisterForm(FlaskForm):
    username= StringField(validators=[InputRequired(), Length(
        min=4, max=20)], render_kw={"placeholder": "Username"})
    password= PasswordField(validators=[InputRequired(), Length(
        min=4, max=20)], render_kw={"placeholder": "Password"})
    submit= SubmitField("Register")

def validate_username(self, username):
        existing_user_username= User.query.filter_by(
            username=username.data).first() 
        with pytest.raises(SQLAlchemy.exc.IntegrityError):
            if existing_user_username:
                raise IntegrityError(
                "That username already exists. Please choose a different one.")
            
class LoginForm(FlaskForm):
    username= StringField(validators=[InputRequired(), Length(
        min=4, max=20)], render_kw={"placeholder": "Username"})
    password= PasswordField(validators=[InputRequired(), Length(
        min=4, max=20)], render_kw={"placeholder": "Password"})
    submit= SubmitField("Register")
    
    
@app.route("/")
def home():
    return render_template('index.html')

@app.route("/login", methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        user= User.query.filter_by(username=form.username.data).first()
        if user:
            if bcrypt.check_password_hash(user.password, form.password.data):
                login_user(user)
                return redirect(url_for('dashboard'))

    return render_template('login.html', form=form)



@app.route("/dashboard", methods=['GET', 'POST'])
@login_required
def dashboard():
    return render_template('dashboard.html')

@app.route('/register', methods=['GET', 'POST'])
def register():
    form = RegisterForm()

    if form.validate_on_submit():
        form.password.data=form.password.data.encode('utf-8')
        hashed_password = bcrypt.generate_password_hash(form.password.data)
        new_user = User(username=form.username.data, password=hashed_password)
        db.session.add(new_user)
        db.session.commit()
        return redirect(url_for('login'))

    return render_template('register.html', form=form)


if __name__ == '__main__':
    app.run()

问题：

什么可能导致“没有这样的表：用户”错误，以及如何解决它以在我的 Flask 应用程序中成功注册用户？

Answer 1

我已经解决了。但现在我面临另一个问题。 此代码不起作用：

def validate_username(self, username):
    existing_user_username= User.query.filter_by(
        username=username.data).first() 
    with pytest.raises(SQLAlchemy.exc.IntegrityError):
        if existing_user_username:
            raise IntegrityError(
            "That username already exists. Please choose a different one.")

当我尝试注册数据库中已存在的用户时，我收到：(sqlite3.IntegrityError) UNIQUE 约束，而不是我放入异常中的约束。