Using a custom JSON encoder for SQLAlchemy's PostgreSQL JSONB implementation

Question

I am using SQLAlchemy\'s core library to access some PostgreSQL database. Consider I have the following table:

create table foo (j jsonb);

Answer 1

This is supported via the json_serializer keyword argument to create_engine, as documented under sqlalchemy.dialects.postgresql.JSON:

def _default(val):
    if isinstance(val, Decimal):
        return str(val)
    raise TypeError()

def dumps(d):
    return json.dumps(d, default=_default)

engine = create_engine(..., json_serializer=dumps)