更新pymongo中的集合

Question

I would like to check the number of document inserted into my collection.

Here is my code in Python:

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()

the problem that after for statement, my result is empty and so the len is null. I don't know what's wrong. Thank you

Answer 1

The collection.aggregate() method returns a CommandCursor , which is kind of like a Python generator that is iterable for only once. Therefore when you call list(result) you will not be able to re-iterate over the cursor.

What you can do instead is to count the number of documents in result within the for loop without creating the array before hand:

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()