更新pymongo中的集合

Question

我想檢查插入收藏夾中的文檔數量。

這是我在Python中的代碼：

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語句后，我的結果為空，因此len為null的問題。 我不知道怎么了 謝謝

Answer 1

collection.aggregate()方法返回一個CommandCursor ，它類似於Python生成器，只能迭代一次。 因此，當您調用list(result)您將無法在光標上再次迭代。

相反，您可以做的是在for循環中計算result中的文檔數，而無需事先創建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()