python – 为什么我在Flask中收到404错误？

在服务器上找不到请求的URL.
如果您手动输入了URL,请检查拼写,然后重试.

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

from datetime import datetime

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////media/workdrive/workspace/purkinje/temp.db'
app.debug = True
db = SQLAlchemy(app)

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

class Post(db.Model):
    id = db.Column(db.Integer,primary_key=True)
    title = db.Column(db.String(80))
    body = db.Column(db.Text)
    pub_date = db.Column(db.DateTime)

    category_id = db.Column(db.Integer,db.ForeignKey('category.id'))
    category = db.relationship('Category',backref=db.backref('posts',lazy='dynamic'))

    def __init__(self,title,body,category,pub_date=None):
        self.title = title
        self.body = body
        if pub_date is None:
            pub_date = datetime.utcnow()
        self.pub_date = pub_date
        self.category = category

    def __repr__(self):
        return '<Post %r>' % self.title

class Category(db.Model):
    id = db.Column(db.Integer,primary_key=True)
    name = db.Column(db.String(50))

    def __init__(self,name):
        self.name = name

    def __repr__(self):
        return '<Category %r> % self.name'

@app.route('/')
def index():
    posts = Post().query.all()
    return render_template('templates/index.html',posts=posts)