Using the $cond statement with $project and aggregate in PyMongo

Question

I want to project a new field based on a conditional logic statement, using pymongo.

The value should equal 1 if the 'status' field is either 'successful_ended' or 'successful_ongoing' . I've tried implementing this by using $in within a $cond statement. A simplified version of my aggregate statement is like so:

pipeline = [
    {'$project': {'platform':1, 'platform_id':1, 'funding_type':1, 'raised_usd':1, 'status':1, 
                  'successful_1': # an equals statement works
                     {
                        '$cond':[{'$eq':['status', 'successful_ended']}, 1, 0]
                     },
                  'successful_2': # but this fails 
                     {
                        '$cond':[{'status': {'$in': ['successful_ended', 'successful_ongoing']}}, 1, 0]
                     }
                  }
    }
]

result = db.projects.aggregate(pipeline)

And it fails with the message:

invalid operator '$in'

What have I done wrong?

Answer 1

Use the $or operator instead which evaluates one or more expressions and returns true if any of the expressions are true. Otherwise, $or returns false. Thus the successful_2 field can be projected as:

'successful_2': {
    '$cond': [ 
        { 
            '$or': [ 
                { '$eq': [ '$status', 'successful_ended' ] }, 
                { '$eq': [ '$status', 'successful_ongoing' ] } 
            ]
        }     
        , 1, 0 
    ]
}

Answer 2

The problem is that there is no $in operator defined for the aggregation framework.

As you can see there are separate $eq operators defined for a regular query and aggregation query , and their syntax is different.

However $in is defined only for a regular query.

If you want to compare a field value against multiple values, you better go with chridam's solution