Pylons 1.0 属性错误：“模块”对象没有属性“元数据”；

Question

Python 新手尝试学习 Pylons。我正在使用 QuickWiki 教程 (http://pylonshq.com/docs/en /1.0/tutorials/quickwiki_tutorial/）来自 1.0 文档，但这个所谓的“1.0”文档似乎只是“0.9.7”；我怀疑这与我收到的错误有关。

当我执行“paster setup-appdevelopment.ini”时，我得到以下信息：

(mydevenv)lucid@lucid-laptop:~/QuickWiki$ paster setup-app development.ini
Traceback (most recent call last):
... edited for brevity...
File "/home/lucid/mydevenv/lib/python2.6/site-packages/setuptools-0.6c11-py2.6.egg/pkg_resources.py", line 1954, in load
File "/home/lucid/QuickWiki/quickwiki/config/middleware.py", line 11, in <module>
from quickwiki.config.environment import load_environment
File "/home/lucid/QuickWiki/quickwiki/config/environment.py", line 12, in <module>
from quickwiki.model import init_model
File "/home/lucid/QuickWiki/quickwiki/model/__init__.py", line 27, in <module>
pages_table = sa.Table('pages', meta.metadata,
AttributeError: 'module' object has no attribute 'metadata'
(mydevenv)lucid@lucid-laptop:~/QuickWiki$

Answer 1

这是文档中的错误 http://pylonshq.com/docs/en/1.0/教程/quickwiki_tutorial/

像这样声明pages_table

from quickwiki.model.meta import Base
pages_table = sa.Table('pages', Base.metadata,
                sa.Column('title', sa.types.Unicode(40), primary_key=True),
                sa.Column('content', sa.types.UnicodeText(), default='')
                )

没有记录器meta.metadata，使用meta.Base.metadata并使用SqlAlchemy声明性基本扩展定义模型http://www.sqlalchemy.org/docs/05/ormtutorial.html#creating -表类和映射器一次全部声明式

Answer 2

您对 estin 答案的评论询问这是否在 SqlAlchemy 0.5 和 0.6 之间发生变化。

事实并非如此。是一样的。现在 Pylons 有不同的默认值。
正如 estin 所说，Pylons 默认创建 declarative_base() ，以便您可以声明性地使用 SqlAlchemy。

class MyRecord(Base):
     __tablename__ = "myrecord"

     id = Column(Integer, primary_key=True)
     data = Column(Unicode, nullable=False)

这不是首先使用 Table() 构造指定表，然后创建类，然后使用 mapper() 将它们映射在一起。

SqlAlchemy Declarative 自动执行此操作。 Quickwiki 告诉您使用 SqlAlchemy 的显式非声明性版本，这是没有理由的（声明性更简洁）。 Pylon 过去将默认元数据公开为 model.meta.metadata，但现在它是由 declarative_base() 创建并在 model.meta.Base.metadata 中公开。

Answer 3

以防万一有人遇到同样的问题，我包括我的 model.init 和 websetup：

"""=========================__init__.py========================="""
    """The application's model objects"""
from quickwiki.model.meta import Session, Base


def init_model(engine):
    """Call me before using any of the tables or classes in the model"""
    Session.configure(bind=engine)

import logging
import re
import sets
from docutils.core import publish_parts

from pylons import url
from quickwiki.lib.helpers import link_to

log = logging.getLogger(__name__)

# disable docutils security hazards:
# http://docutils.sourceforge.net/docs/howto/security.html
SAFE_DOCUTILS = dict(file_insertion_enabled=False, raw_enabled=False)
wikiwords = re.compile(r"\b([A-Z]\w+[A-Z]+\w+)", re.UNICODE)

from sqlalchemy import orm
import sqlalchemy as sa

pages_table = sa.Table('pages', Base.metadata,
                sa.Column('title', sa.types.Unicode(40), primary_key=True),
                sa.Column('content', sa.types.UnicodeText(), default='')
                )

class Page(object):

    def __init__(self, title, content=None):
        self.title = title
        self.content = content

    def get_wiki_content(self):
        """Convert reStructuredText content to HTML for display, and
        create links for WikiWords
        """
        content = publish_parts(self.content, writer_name='html',
                                settings_overrides=SAFE_DOCUTILS)['html_body']
        titles = sets.Set(wikiwords.findall(content))
        for title in titles:
            title_url = url(controller='pages', action='show', title=title)
            content = content.replace(title, link_to(title, title_url))
        return content

    def __unicode__(self):
        return self.title

    __str__ = __unicode__

orm.mapper(Page, pages_table)

"""=========================websetup.py========================="""

"""Setup the QuickWiki application"""
import logging

import pylons.test

from quickwiki.config.environment import load_environment
from quickwiki.model.meta import Session, Base
from quickwiki import model

log = logging.getLogger(__name__)

def setup_app(command, conf, vars):
    """Place any commands to setup quickwiki here"""
    load_environment(conf.global_conf, conf.local_conf)

    # Create the tables if they don't already exist
    log.info("Creating tables...")
    Base.metadata.create_all(bind=Session.bind)
    log.info("Successfully set up.")

    log.info("Adding front page data...")
    page = model.Page(title=u'FrontPage',
                      content=u'**Welcome** to the QuickWiki front page!')

    Session.add(page)
    Session.commit()
    log.info("Successfully set up.")