Question

所以我不太明白这里究竟是什么问题。我正在使用python-flask，目前正试图从我的Post模型调用某些帖子。但是，我总是得到这个“peewee.OperationalError：near”AS“：语法错误”错误消息，这是由我的用户模型中的以下类方法引起的：

    @classmethod 
    def get_stream(self):
        return Post.select().where(Post.user == self)

我在以下路径中调用此方法来定义流，然后将其传递给模板：

@app.route('/stream')
@app.route('/stream/<username>')
def stream(username=None):
    template = 'stream.html'
    if username and username != current_user.username:
        user = social.User.select().where(social.User.username**username).get()
        stream = user.posts.limit(100)
    else:
        stream = current_user.get_stream().limit(100)
        user = current_user
    if username:
        template = "user_stream.html"
#   stream = social.Post.select().where(social.Post.user == current_user.id)
    return render_template(template, stream=stream, user=user)

使用当前评论的行它可以正常工作，但没有它我得到错误。所以这肯定是一个问题

任何人都知道问题是什么？

供参考，以下是User和Post模型：

class User(UserMixin, Model):
    username = CharField(unique=True)
    email = CharField(unique=True)
    password = CharField(max_length=100)
    joined_at = DateTimeField(default=datetime.datetime.now)
    is_admin = BooleanField(default=False)

    class Meta:
        database = USER_DB
        order_by = ('joined_at',)

    @classmethod 
    def get_stream(self):
        return Post.select().where(Post.user == self)

    @classmethod
    def create_user(cls, username, email, password, admin=False):
        try:
            with USER_DB.transaction():
                cls.create(
                    username=username,
                    email=email,
                    password=generate_password_hash(password),
                    is_admin=admin)
        except IntegrityError:
            raise ValueError("User already exists.")


class Post(Model):
    timestamp = DateTimeField(default=datetime.datetime.now)
    user = ForeignKeyField(
        rel_model=User,
        related_name='posts'
        )
    content = TextField()

    class Meta:
        database = USER_DB
        order_by = ('-timestamp',)

追踪（最近一次调用最后一次）

File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/_compat.py", line 33, in reraise
raise value
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/_compat.py", line 33, in reraise
raise value
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/SuperMario/Desktop/treehouse/flask_track/simple_app.py", line 49, in stream
return render_template(template, stream=stream, user=user)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/templating.py", line 128, in render_template
context, ctx.app)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/flask/templating.py", line 110, in _render
rv = template.render(context)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/jinja2/environment.py", line 989, in render
return self.environment.handle_exception(exc_info, True)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/jinja2/environment.py", line 754, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/jinja2/_compat.py", line 37, in reraise
raise value.with_traceback(tb)
File "/Users/SuperMario/Desktop/treehouse/flask_track/templates/user_stream.html", line 1, in top-level template code
{% extends "stream.html" %}
File "/Users/SuperMario/Desktop/treehouse/flask_track/templates/stream.html", line 1, in top-level template code
{% extends "layout.html" %}
File "/Users/SuperMario/Desktop/treehouse/flask_track/templates/layout.html", line 25, in top-level template code
{% block content %}     {% endblock %}
File "/Users/SuperMario/Desktop/treehouse/flask_track/templates/user_stream.html", line 26, in block "content"
{{ super() }}
File "/Users/SuperMario/Desktop/treehouse/flask_track/templates/stream.html", line 5, in block "content"
{% for post in stream %}
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 2866, in __iter__
return iter(self.execute())
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 2859, in execute
self._qr = ResultWrapper(model_class, self._execute(), query_meta)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 2555, in _execute
return self.database.execute_sql(sql, params, self.require_commit)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 3366, in execute_sql
Open an interactive python shell in this frameself.commit()
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 3212, in __exit__
reraise(new_type, new_type(*exc_args), traceback)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 125, in reraise
raise value.with_traceback(tb)
File "/Users/SuperMario/Desktop/treehouse/treehouse_flask_track/lib/python3.4/site-packages/peewee.py", line 3359, in execute_sql
cursor.execute(sql, params or ())

Answer 1

用@classmethod装饰方法告诉Python传递类而不是实例作为第一个参数。通常，在这种情况下，您将第一个参数命名为cls以保持清晰。

您的方法正在尝试使用调用它的用户实例获取所有Post，而是调用该方法传递User类。删除@classmethod装饰器。

def get_stream(self):
    return Post.select().where(Post.user == self)

现在self是一个用户实例，关系Post.user == self是有道理的。

Answer 2

在@classmethod模型中定义方法之前User阻止了它的工作。我仍然需要弄清楚原因，但现在它可行。

peewee.OperationalError：“AS”附近：语法错误

2 个答案: