PyMongo 奇怪错误“TypeError:“Database”对象不可调用。”

Question

我遇到了一个奇怪的错误。

来源： __init__.py

import os
import base64
import uuid

import tornado.web
import tornado.httpserver
import tornado.locale
import tornado.ioloop
import tornado.options

from tornado.options import define, options

from pymongo.connection import Connection
from pymongo.database import Database

from handlers import api
#from auth import AuthLoginHandler
#from auth import AuthLogoutHandler
#from auth import AuthFirstRunHandler
from handlers import home

## Options
define("listen_port",       default = 7456, type = "int", 
                help = "bind to port")

define("listen_address",    default = None, type = "string",
                help = "bind to address")

define("static_path",       default = os.path.join(os.path.dirname(__file__), "static"), type = "string",
                help = "directory to store static resource")

# http://www.v2ex.com/t/12646
define("cookie_secret",     default = base64.b64encode(uuid.uuid4().bytes + uuid.uuid4().bytes), type = "string",
                help = "cookie")

define("mongo_host",        default = "127.0.0.1", type = "string",
                help = "hostname or ip of mongo host")

define("mongo_port",        default = 27017, type = "int",
                help = "port of mongo host")

define("mongo_collection",  default = "meowth", type = "string",
                help = "collection name")

tornado.options.parse_command_line()

class Application(tornado.web.Application):
    def __init__(self):
        tornado.web.Application.__init__(self, [
            (r"/i", home.HomeHandler),
        #   (r"/auth/login", AuthLoginHandler),
        #   (r"/auth/logout", AuthLogoutHandler),
        #   (r"/auth/install", AuthFirstRunHandler),
        #   (r"/backstage", BackstageHomeHandler),
            (r"/api/cluster", api.APIHandler),
            (r"/api/user", api.APIHandler),
            (r"/api/connection", api.APIHandler),
            (r"/api/control", api.APIHandler),
            (r"/static/(.*)", tornado.web.StaticFileHandler, { "path" : options.static_path })
        ],** dict(
            xsrf_cookies = True,
            cookie_secret = options.cookie_secret
        ))

        # init database connection
        self.mongo = Database(
            Connection(
                options.mongo_host,
                options.mongo_port
            ),
            options.mongo_collection
        )
        #self.mongo = self.mongoConnection[options.mongo_collection]
        #self.mongo = self.mongoConnection.meowth

def main():
    if options.listen_address == None:
        tornado.httpserver.HTTPServer(Application()).listen(options.listen_port)
    else:
        tornado.httpserver.HTTPServer(Application()).listen(options.listen_port, address = options.listen_address)

    tornado.ioloop.IOLoop.instance().start()

if __name__ == "__main__":
    main()

base.py

# -*- coding: utf8 -*-
import tornado.web
import pymongo

class BaseHandler(tornado.web.RequestHandler):

    def __init__(self, application, request, **kwargs):
        tornado.web.RequestHandler.__init__(self, application, request, **kwargs)
        self.session_id = self.get_secure_cookie("meowth_session")
        self.session = {}

    @property
    def db(self):
        print self.application.mongo
        return self.application.mongo

    def init_session(self):
        if not self.session_id:
            self.session_id = self.db().meowth_sessions.save(
                {"data" : self.session}
            )
        else:
            self.session = self.db().meowth_sessions.find_one(
                {"_id" : self.session_id}
            )

    def flush_session(self):
        self.db().meowth_sessions.save(
                {"data" : self.session,
                 "_id"  : self.session_id
                }
            )

    def is_spider(self):
        # https://bitbucket.org/keakon/doodle/src/3ddf46ac59e7/zh-CN/common.py#cl-512
        user_agent = self.request.headers["User-Agent"]
        if 'bot' in user_agent or 'spider' in user_agent:
            return True
        return False

错误：

> [root@CloudK02 Meowth]# ./Meowth-Web Database(Connection('127.0.0.1',
> 27017), u'meowth') [E 120219 15:07:54 web:1031] Uncaught exception GET
> /i (122.94.31.186)
>     HTTPRequest(protocol='http', host='us1.loli.vg:7456', method='GET', uri='/i', version='HTTP/1.1', remote_ip='122.94.31.186',
> body='', headers={'Accept-Language': 'en-US,en;q=0.8',
> 'Accept-Encoding': 'gzip,deflate,sdch', 'Host': 'us1.loli.vg:7456',
> 'Accept':
> 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
> 'User-Agent': 'Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.11 (KHTML,
> like Gecko) Chrome/17.0.963.56 Safari/535.11', 'Accept-Charset':
> 'ISO-8859-1,utf-8;q=0.7,*;q=0.3', 'Connection': 'keep-alive',
> 'Cookie': 'PHPSESSID=rm4ght6ivop9a1hf5oogcft3j4;
> session_id="MzZkODNiMWMyZjczOWZhNzcxYjU4YTNjNzVhZjA4Yzc=|1329674350|2562f7ed871c1ca3e24dcb5891d6e753cfacfa44";
> rock_format=json', 'Cache-Control': 'max-age=0'})
>     Traceback (most recent call last):
>       File "/usr/local/lib/python2.6/site-packages/tornado/web.py", line 988, in _execute
>         getattr(self, self.request.method.lower())(*args, **kwargs)
>       File "/home/aveline/Meowth/web/handlers/home.py", line 7, in get
>         self.init_session()
>       File "/home/aveline/Meowth/web/handlers/base.py", line 19, in init_session
>         self.session_id = self.db().meowth_sessions.save(
>       File "build/bdist.linux-x86_64/egg/pymongo/database.py", line 696, in __call__
>         "failing because no such method exists." % self.__name)
>     TypeError: 'Database' object is not callable. If you meant to call the 'meowth' method on a 'Connection' object it is failing because no
> such method exists.

如果我在 Application 类中使用 self.mongo，效果很好。 但是如果我在 BaseHandler 类中使用它，就会出现错误。

为什么？

Answer 1

您已将 db 定义为属性，这意味着您不必调用它。但后来你就打电话了！

删除 @property 或使用 self.db 而不是 self.db()。

---

与往常一样，Python 的错误消息提供了丰富的信息，您应该查看它们！在这种情况下，您可以看到

TypeError: 'Database' object is not callable. If you meant to call the 'meowth' method on a 'Connection' object it is failing because no such method exists.

这意味着您正在某处调用（即像函数一样）数据库对象。在哪里？

File "/home/aveline/Meowth/web/handlers/base.py", line 19, in init_session
    self.session_id = self.db().meowth_sessions.save(

看？ self.db 是一个属性，因此为您提供 self.application.mongo。然后你调用它，所以上面这行相当于

self.session_id = self.application.mongo().meowth_sessions.save(

这显然是错误的。