How to convert unicode to koi8-r?

[AlekseyPython]

Python 3.7.2

I write data to the database, so I want to write lines in a format that has a low weight. One character of the Russian language in utf8 occupies 2 bytes, and in the koi8-r encoding only 1 byte (I am only interested in Russian and English alphabets, the other characters can be ignored).

When in Python I convert the English- Russian string to koi8-r, I get a strange sequence:

utf = 'My string, Моя строка'
koi = utf.encode(encoding='koi8-r', errors='ignore')

Output:
koi	bytes: b'My string, \\xed\\xcf\\xd1 \\xd3\\xd4\\xd2\\xcf\\xcb\\xc1'	

When I write these values ​​to the database, I get write- errors.
How I can convert data in 'small format'?