database 在 MongoDB 的 pymongo 中，我如何执行 count()？
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In MongoDB's pymongo, how do I do a count()?
提问by TIMEX
for post in db.datasets.find({"test_set":"abc"}).sort("abc",pymongo.DESCENDING).skip((page-1)*num).limit(num):
This is my current code.
这是我目前的代码。
How do I get the count() ?
我如何获得 count() ？
回答by thirtydot
If you're using pymongo version 3.7.0 or higher, see this answerinstead.
如果您使用的是 pymongo 3.7.0 或更高版本，请参阅此答案。
If you want results_countto ignore your limit():
如果你想results_count忽略你的limit()：
results = db.datasets.find({"test_set":"abc"}).sort("abc",pymongo.DESCENDING).skip((page-1)*num).limit(num)
results_count = results.count()
for post in results:
If you want the results_countto be capped at your limit(), set applySkipLimitto True:
如果您希望results_count将 限制在您的limit()，请设置applySkipLimit为True：
results = db.datasets.find({"test_set":"abc"}).sort("abc",pymongo.DESCENDING).skip((page-1)*num).limit(num)
results_count = results.count(True)
for post in results:
回答by Sohaib Farooqi
Since pymongo version 3.7.0 and above count() is deprecated. Instead use Collection.count_documents. Running cursor.countor collection.countwill result in following warning message:
由于 pymongo 3.7.0 及以上版本count() 已弃用。而是使用Collection.count_documents。运行cursor.count或collection.count将导致以下警告消息：
DeprecationWarning: count is deprecated. Use Collection.count_documents instead.
To use count_documentsthe code can be adjusted as follows
使用count_documents代码可以调整如下
import pymongo
db = pymongo.MongoClient()
col = db[DATABASE][COLLECTION]
filter = {"test_set":"abc"}
sort = [("abc",pymongo.DESCENDING)]
skip = 10
limit = 10
doc_count = col.count_documents(filter, skip=skip)
results = col.find(filter).sort(sort).skip(skip).limit(limit)
for doc in result:
//Process Document
Note:count_documentsmethod performs relatively slow as compared to countmethod. In order to optimize you can use collection.estimated_document_count. This method will return estimated number of docs(as the name suggested) based on collection metadata.
注意：count_documents与count方法相比，方法的执行速度相对较慢。为了优化您可以使用collection.estimated_document_count. 此方法将根据集合元数据返回估计的文档数量（如建议的名称）。
回答by None-da
Not sure why you want the count if you are already passing limit 'num'. Anyway if you want to assert, here is what you should do.
如果您已经通过了限制“num”，不确定为什么要计数。无论如何，如果你想断言，这就是你应该做的。
results = db.datasets.find({"test_set":"abc"}).sort("abc",pymongo.DESCENDING).skip((page-1)*num).limit(num)
results_count = results.count(True)
That will match results_countwith num
这将匹配results_count与num
