DictCursor for psycopg 3

dicttuple.py

class DictTuple(tuple):
    """Tuple class with added item getting by name.
    """
    def __new__(cls, d):
        rv = super().__new__(cls, d.values())
        rv._map = d
        return rv

    def __repr__(self):
        return f"{type(self).__qualname__}({self._map!r})"

    def __getitem__(self, key):
        if isinstance(key, str):
            return self._map[key]
        else:
            return super().__getitem__(key)


def dicttuple_row(cursor):
    """psycopg 3 row factory to return DictTuple.
    
    Simulate psycopg2 DictCursor.
    """
    desc = cursor.description
    assert desc, "no result available"

    names = [c.name for c in desc]

    def dicttuple_row_(values):
        return DictTuple(dict(zip(names, values)))

    return dicttuple_row_


if __name__ == "__main__":
    import psycopg

    conn = psycopg.connect("", row_factory=dicttuple_row)
    row = conn.execute("select 10 as foo, 20 as bar").fetchone()
    print(f"{row=}")
    # row=DictTuple({'foo': 10, 'bar': 20})
    print(f"{row['foo']=}")
    # row['foo']=10
    print(f"{row[1]=}")
    # row[1]=20
    a, b = row
    print(f"{a=}, {b=}")
    # a=10, b=20