更新pymongo中的集合

Question

我想检查插入收藏夹中的文档数量。

这是我在Python中的代码：

from pymongo import MongoClient
connection = MongoClient()
db = connection['mydatabase']
collection1 = db.mycollection
collection2=db.mycollection1
pipe = [{......}]
result = collection1.aggregate(pipe, allowDiskUse=True)

array = list(result)
length = len(array)

for res in result:
    id = res['_id']
    collection2.update({..}, upsert=True)
count = collection2.find().count()
print ("There are %d documents in users collection" %count)

if length == count:
     print("insertion ok")
else:
     print("echec")

connection.close()

for语句后，我的结果为空，因此len为null的问题。 我不知道怎么了 谢谢

Answer 1

collection.aggregate()方法返回一个CommandCursor ，它类似于Python生成器，只能迭代一次。 因此，当您调用list(result)您将无法在光标上再次迭代。

相反，您可以做的是在for循环中计算result中的文档数，而无需事先创建array ：

from pymongo import MongoClient
connection = MongoClient()
db = connection['mydatabase']
collection1 = db.mycollection
collection2 = db.mycollection1
pipe = [{......}]
result = collection1.aggregate(pipe, allowDiskUse=True)

length = 0
for res in result:
    id = res['_id']
    collection2.update({..}, upsert=True)
    length += 1

count = collection2.count()
print ("There are %d documents in users collection" %count)

if length == count:
    print("insertion ok")
else:
    print("echec")

connection.close()