comprehension list in pymongo query

Question

Good morning everyone,

I would like to write a pymongo snippet to query from a database all documents having a specific field value within a given list (so also a value which is a subset of any element in the given list).

Within python, I would have two lists and I would like to find all elements from list one which are contained in at least one element from list two. Eg:

list1 = ['abc', 'bob', 'joe_123']
list2 = ['abc', 'joe', 'mike']
for string in list2:
    print( string, any([ string in xxx for xxx in list1 ]) )

which gives the correct result:

abc True
joe True
mike False

How could I get the same from pymongo? I tried the "$in" operator, but the result is not complete.

from pymongo import MongoClient
from pprint import pprint

client = MongoClient('mongodb://localhost:27017')
db = client['test_query']
my_coll = db['test_collection']

list1 = ['abc', 'bob', 'joe_123']
list2 = ['abc', 'joe', 'mike']

for string in list2:
    my_coll.insert_one({'string' : string})

cursor = my_coll.find({'string' : { '$in' : list1} })
which misses the case in joe < joe_123

pprint([c for c in cursor])
[{'_id': ObjectId('5f60ce9b682ff1bf4dcafb94'), 'string': 'abc'}]

Could anyone give me a hint on this?

More generally, what is the syntax to incorporate a python comprehension list into a pymongo query?

Thank you so much

Marco

Answer 1

$in in mongodb does not match on a partial string.

To do this you must use $regex , eg

for string in list1:
    my_coll.insert_one({'string' : string})

query = {'$regex': '|'.join(list2)}
cursor = my_coll.find({'string' : query})

pprint([c for c in cursor])