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

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

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

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}
})