pymongo find() 与 mongodb find()，pymongo find() 提供的关于文档的数据较少
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pymongo find() vs mongodb find(), pymongo find() gives less data about document
提问by daydreamer
I have a partner collectionand I am using pymongoto retrieve the data
When I query the collection with MongoDB, I see the following result
我有一个partner collection，我正在使用它pymongo来检索数据
当我使用MongoDB查询集合时，我看到以下结果
db.partner.find({'unique_key': 'c89dbe313932008febde61cdd2a071a1d'},{})
{ "_id" : ObjectId("4eb463cb158acb554e8c9c11"), "unique_key" : "c89dbe313932008febde61cdd2a071a1d", "name" : "ABC", "primary_key" : 12 }
But when I query via pymongo, here is what I do
但是当我通过pymongo查询时，这就是我所做的
for document in collection.find(find, criteria):
print document
where find = {'unique_key': 'c89dbe313932008febde61cdd2a071a1d'} and
criteria = {}
Here is what I see in result:
这是我在结果中看到的：
{u'_id': ObjectId('4eb463cb158acb554e8c9c11')}
and I don't get nameand primary_keyin result, am I missing something?
我没有得到name和primary_key结果，我错过了什么吗？
Thank you
谢谢
回答by Lycha
It seems that when you pass empty dictionary (your criteriavariable) as the second parameter it means you want no fields returned (except _idthat is always returned). The second parameter for find()defines the fields that you want. Try to set criteria=Noneor not pass criteriaat all.
似乎当您将空字典（您的criteria变量）作为第二个参数传递时，这意味着您不希望返回任何字段（除非_id始终返回）。的第二个参数find()定义了您想要的字段。尝试设置criteria=None或根本不通过criteria。
Linkto the pymongo document for find().
链接到 pymongo 文档find()。
回答by dcrosta
This is due to how the mongodb shell interprets {}as a field selector vs. how pymongo interprets an empty dictionary. In essence, the shell ignores the empty object as a field selector, whereas pymongo is interpreting it as "return nothing (except the default of _id)".
这是由于 mongodb shell 如何解释{}为字段选择器与 pymongo 如何解释空字典。本质上，shell 忽略空对象作为字段选择器，而 pymongo 将其解释为“不返回任何内容（除了默认值_id）”。
You don't need to specify a field selector when using pymongo or the mongodb shell (you can just leave it blank). Thus, this statement in the shell:
使用 pymongo 或 mongodb shell 时不需要指定字段选择器（您可以将其留空）。因此，shell 中的这个语句：
db.partner.find({'unique_key': 'c89dbe313932008febde61cdd2a071a1d'},{})
is equivalent to:
相当于：
db.partner.find({'unique_key': 'c89dbe313932008febde61cdd2a071a1d'})
(this statement will work in both the shell and pymongo)
（这个语句在 shell 和 pymongo 中都有效）
