为什么我试图通过pymongo查询我的mongodb数据库时得到一个pymongo.cursor.Cursor？ [英] Why do I get a pymongo.cursor.Cursor when trying to query my mongodb db via pymongo?

问题描述

我在一个mongodb数据库中消耗了一些tweets。我想使用pymongo查询这些tweet。例如，我想查询screen_name。但是，当我尝试这样做，python不返回tweet，但是关于pymongo.cursor.Cursor的消息。这是我的代码：

I have consumed a bunch of tweets in a mongodb database. I would like to query these tweets using pymongo. For example, I would like to query for screen_name. However, when I try to do this, python does not return a tweet but a message about pymongo.cursor.Cursor. Here is my code:

import sys
import pymongo
from pymongo import Connection
connection = Connection()
db = connection.test
tweets = db.tweets
list(tweets.find())[:1]

我得到一个JSON，如下所示：

I get a JSON, which looks like this:

{u'_id': ObjectId('51c8878fadb68a0b96c6ebf1'),
 u'contributors': None,
 u'coordinates': {u'coordinates': [-75.24692983, 43.06183036],
  u'type': u'Point'},
 u'created_at': u'Mon Jun 24 17:53:19 +0000 2013',
 u'entities': {u'hashtags': [],
  u'symbols': [],
  u'urls': [],
  u'user_mentions': []},
 u'favorite_count': 0,
 u'favorited': False,
 u'filter_level': u'medium',
 u'geo': {u'coordinates': [43.06183036, -75.24692983], u'type': u'Point'},
 u'id': 349223725943623680L,
 u'id_str': u'349223725943623680',
 u'in_reply_to_screen_name': None,
 u'in_reply_to_status_id': None,
 u'in_reply_to_status_id_str': None,
 u'in_reply_to_user_id': None,
 u'in_reply_to_user_id_str': None,
 u'lang': u'en',
 u'place': {u'attributes': {},
  u'bounding_box': {u'coordinates': [[[-79.76259, 40.477399],
     [-79.76259, 45.015865],
     [-71.777491, 45.015865],
     [-71.777491, 40.477399]]],
   u'type': u'Polygon'},
  u'country': u'United States',
  u'country_code': u'US',
  u'full_name': u'New York, US',
  u'id': u'94965b2c45386f87',
  u'name': u'New York',
  u'place_type': u'admin',
  u'url': u'http://api.twitter.com/1/geo/id/94965b2c45386f87.json'},
 u'retweet_count': 0,
 u'retweeted': False,
 u'source': u'<a href="http://twitter.com/download/iphone" rel="nofollow">Twitter for iPhone</a>',
 u'text': u'Currently having a heat stroke',
 u'truncated': False,
 u'user': {u'contributors_enabled': False,
  u'created_at': u'Fri Oct 28 02:04:05 +0000 2011',
  u'default_profile': False,
  u'default_profile_image': False,
  u'description': u'young and so mischievious',
  u'favourites_count': 1798,
  u'follow_request_sent': None,
  u'followers_count': 368,
  u'following': None,
  u'friends_count': 335,
  u'geo_enabled': True,
  u'id': 399801173,
  u'id_str': u'399801173',
  u'is_translator': False,
  u'lang': u'en',
  u'listed_count': 0,
  u'location': u'Upstate New York',
  u'name': u'Joe Catanzarita',
  u'notifications': None,
  u'profile_background_color': u'D6640D',
  u'profile_background_image_url':           u'http://a0.twimg.com/profile_background_images/702001815/f87508e73bbfab8c8c85ebe10b29fcf6.png',
  u'profile_background_image_url_https':     u'https://si0.twimg.com/profile_background_images/702001815/f87508e73bbfab8c8c85ebe10b29fcf6.png',
  u'profile_background_tile': True,
  u'profile_banner_url': u'https://pbs.twimg.com/profile_banners/399801173/1367200323',
  u'profile_image_url':     u'http://a0.twimg.com/profile_images/378800000012256721/d8b5f801fb331de6ead4aed42dc77a46_normal.jpeg',
  u'profile_image_url_https':   u'https://si0.twimg.com/profile_images/378800000012256721/d8b5f801fb331de6ead4aed42dc77a46_normal.jpeg'    ,
  u'profile_link_color': u'140DE0',
  u'profile_sidebar_border_color': u'FFFFFF',
  u'profile_sidebar_fill_color': u'E0F5A6',
  u'profile_text_color': u'120212',
  u'profile_use_background_image': True,
  u'protected': False,
  u'screen_name': u'JoeCatanzarita',
  u'statuses_count': 6402,
  u'time_zone': u'Quito',
  u'url': None,
  u'utc_offset': -18000,
  u'verified': False}}

但是，当我尝试查询这个screen_name时，我得到：

However, when I try to query for this screen_name, I get:

tweets.find({"screen_name": "JoeCatanzarita"})
<pymongo.cursor.Cursor at 0x52c02f0>

然后当我尝试计算有screen_name：name的tweets数时，我得到：

And when I then try to count the number of tweets which have "screen_name": "name", I get:

tweets.find({"screen_name": "name"}).count()
0

任何想法我做错了/我怎么能得到pymongo返回我正在寻找的tweets ？

Any idea what I am doing wrong/how I can get pymongo to return the tweets I am looking for?

谢谢！

推荐答案

：

如果你仔细看看你的文档，你会注意到screen_name是在子文档用户里面，所以如果你想接受它，你所要做的就是以下：

If you look carefully into your document you will notice that "screen_name" is inside the subdocument user, so if you want to acess it all you have to do is the following:

tweets.find({"user.screen_name": "JoeCatanzarita"})  #for example.

无论何时，当你正在尝试找到的元素在一个子文档情况或数组内部始终使用此语法。

Whenever you are in a situation where the element you are trying to find is inside a subdocument like in this situation or inside an array always use this syntax.

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