Closest match per group with sqlite3 in python?

I asked preciously how to find closest match, but I later I realized that sql-server ROW_NUMBER and PARTITION BY is not implemented in sqlite3 in python script.

Here is what I am trying to do:

I have table that looks similar to this:

Motor MotorType CalibrationValueX CalibrationValueY
A     Car       1.2343            2.33343
B     Boat      1.2455            2.55434
B1    Boat      1.4554            2.11211
C     Car       1.4323            4.56555
D     Car       1.533             4.6666
..... 500 entries

In my SQL query, I am trying to find average of CalibrationValueY where CalibrationValueX is a certain value:

SELECT avg(CalibrationValueY), MotorType, Motor FROM MotorTable
WHERE CalibrationValueX = 1.23333
GROUP BY MotorType

This will not return anything, since there is not a CalibrationValueX value that equals exactly 1.23333.

I am able to find closest match separately for each MotorTable with:

SELECT CalibrationValueY, FileSize, MotorType, Motor FROM MotorTable
where FileType = 'text' order by abs(FileSize - 1.23333) LIMIT 1

However, I can't get it to work with a group by statement. How can I do it so that if I am grouping by MotorType and I am searching CalibrationValueX = 1.23333, I would get this:

A     Car       1.2343            2.33343
B     Boat      1.2455            2.55434

The solution with row_count and partition by does not work in sqlite3, as I realized.

with cte as (
    SELECT MotorType, CalibrationValueX, CalibrationValueY,
        ROW_NUMBER() over (partition by MotorType order by abs(CalibrationValueX - 1.23333)) rn
    from historyCR
)
SELECT *
from cte
where rn = 1

Alternatively... I could just execute working code X types per each MotorType... Something like SELECT DISTINCT MotorType FROM MotorTable and run other query in a loop. However, I am concerned about speed.