Correct use of $ne or $not in pymongo (unsupported projection option)

Question

I would like to write the following query in Mongo:

Get all rows where field equals var1 but/and not var2

I have this:

db["mydb"].find(
    {"field": var1},
    {"field": {
        "$ne": var2}
    }
)

But it yields the error that $ne is an "unsupported projection option."

Answer 1

You can use the $and operator to combine requirements like this:

db["mydb"].find(
    {"$and": [
        {"field": var1},
        {"field": {
            "$ne": var2
        }}
    ]}
)

Answer 2

Apart from the usage of $and, you can also fix it by using {} to combine the filters.

db["mydb"].find({
    "field": var1,
    "field": {"$ne": var2}
})