Python 如何将 pymongo.cursor.Cursor 转换为 dict？
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How to convert a pymongo.cursor.Cursor into a dict?
提问by gladys0313
I am using pymongo to query for all items in a region (actually it is to query for all venues in a region on a map). I used db.command(SON())before to search in a spherical region, which can return me a dictionary and in the dictionary there is a key called resultswhich contains the venues. Now I need to search in a square area and I am suggested to use db.places.find, however, this returns me a pymongo.cursor.Cursorclass and I have no idea how to extract the venue results from it.
我正在使用 pymongo 查询一个区域内的所有项目（实际上是查询地图上一个区域内的所有场地）。我db.command(SON())以前在一个球形区域中搜索，它可以返回一个字典，在字典中有一个results包含场地的键。现在我需要在一个正方形区域中搜索，我建议使用db.places.find，但是，这会返回一个pymongo.cursor.Cursor类，我不知道如何从中提取场地结果。
Does anyone know whether I should convert the cursor into a dict and extract the results out, or use another method to query for items in a square region? BTW, db is pymongo.database.Database class
有谁知道我是否应该将光标转换为字典并将结果提取出来，或者使用另一种方法来查询方形区域中的项目？顺便说一句，db 是 pymongo.database.Database 类
The codes are:
代码是：
>>> import pymongo
>>> db = pymongo.MongoClient(host).PSRC
>>> resp = db.places.find({"loc": {"$within": {"$box": [[ll_lng,ll_lat], [ur_lng,ur_lat]]}}})
>>> for doc in resp:
>>> print(doc)
I have values of ll_lng, ll_lat, ur_lng and ur_lat, use these values but it prints nothing from this codes
我有 ll_lng、ll_lat、ur_lng 和 ur_lat 的值，使用这些值但它不会从这些代码中打印任何内容
采纳答案by styvane
The findmethod returns a Cursorinstance, which allows you to iterate over all matching documents.
该find方法返回一个Cursor实例，它允许您遍历所有匹配的文档。
To get the first document that matches the given criteria you need to use find_one. The result of find_oneis a dictionary.
要获取与给定条件匹配的第一个文档，您需要使用find_one. 的结果find_one是一本字典。
You can always use the listconstructor to return a list of all the documents in the collection but bear in mind that this will load all the data in memory and may not be what you want.
您始终可以使用list构造函数返回集合中所有文档的列表，但请记住，这会将所有数据加载到内存中，并且可能不是您想要的。
You should do that if you need to reuse the cursor and have a good reason not to use rewind()
如果您需要重用游标并且有充分的理由不使用，则应该这样做 rewind()
Demo using find:
演示使用find：
>>> import pymongo
>>> conn = pymongo.MongoClient()
>>> db = conn.test #test is my database
>>> col = db.spam #Here spam is my collection
>>> cur = col.find()
>>> cur
<pymongo.cursor.Cursor object at 0xb6d447ec>
>>> for doc in cur:
... print(doc) # or do something with the document
...
{'a': 1, '_id': ObjectId('54ff30faadd8f30feb90268f'), 'b': 2}
{'a': 1, 'c': 3, '_id': ObjectId('54ff32a2add8f30feb902690'), 'b': 2}
Demo using find_one:
演示使用find_one：
>>> col.find_one()
{'a': 1, '_id': ObjectId('54ff30faadd8f30feb90268f'), 'b': 2}
回答by Alexandre
The MongoDB findmethod does not return a single result, but a list of results in the form of a Cursor. This latter is an iterator, so you can go through it with a forloop.
MongoDBfind方法不返回单个结果，而是以Cursor. 后者是一个迭代器，所以你可以用一个for循环来遍历它。
For your case, just use the findOnemethod instead of find. This will returns you a single document as a dictionary.
对于您的情况，只需使用该findOne方法而不是find. 这将返回一个作为字典的文档。
回答by Yegor Dia
to_dict()Convert a SON document to a normal Python dictionary instance.
to_dict()将 SON 文档转换为普通的 Python 字典实例。
This is trickier than just dict(...) because it needs to be recursive.
这比 dict(...) 更棘手，因为它需要递归。
回答by Saravanan Subramanian
I suggest create a list and append dictionary into it.
我建议创建一个列表并将字典附加到其中。
x = []
cur = db.dbname.find()
for i in cur:
x.append(i)
print(x)
Now x is a list of dictionary, you can manipulate the same in usual python way.
现在 x 是一个字典列表，你可以用通常的 python 方式操作它。
回答by Aminah Nuraini
Easy
简单
import pymongo
conn = pymongo.MongoClient()
db = conn.test #test is my database
col = db.spam #Here spam is my collection
array = list(col.find())
print array
There you go
你去吧
回答by Rafal
Map function is fast way to convert big collection
Map函数是转换大集合的快速方法
from time import time
cursor = db.collection.find()
def f(x):
return x['name']
t1 = time()
blackset = set(map(f, cursor))
print(time() - t1)
