How to correctly specify the encoding in Python3?

Question

Python

Hello! Help me please. I'm still quite new to Python.
You need to create a transliterator from Cyrillic to Latin.
However, I am adding new characters to the alphabet, different diacritics. I am getting an encoding related error. How to fix it?

Traceback (most recent call last):
  File "C:\Users\Лариса\Desktop\Фото и документы\Математика и инфа\module.py", line 56, in <module>
    print(latinizator(line, legend), end='')
  File "C:\Users\Лариса\AppData\Local\Programs\Python\Python36-32\lib\encodings\cp1251.py", line 19, in encode
    return codecs.charmap_encode(input,self.errors,encoding_table)[0]
UnicodeEncodeError: 'charmap' codec can't encode character '\xed' in position 18: character maps to <undefined>

Here is my code. The number of characters has been reduced to make it look shorter.

import os
import fileinput

def latinizator(letter, dic):
    for i, j in dic.items():
        letter = letter.replace(i, j)
    return letter

legend = {
    
'Ё':'Ö',
'Ж':'Ž',
'З':'Z',
'И':'I',
'Й':'Î',
'Ч':'Č',
'Ш':'Š',
'Щ':'Ś',
'Ъ':'V',
'Ы':'Y',
'Ь':'V',
'Э':'E',
'Ю':'Ü',
'Я':'Ä',

#Дополнительные знаки 
'ий':'í',
'ую':'ú',
'ой':'ó',
'ей':'é',
'ая':'á',
'ть':'ć',
}

with fileinput.FileInput('C:\\Users\\Лариса\\Desktop\\Фото и документы\\Математика и инфа\\alphabet.txt', inplace=True, backup='.bak') as f:
    for line in f:
        print(latinizator(line, legend), end='')

Answer 1

everything seems to work as intended
, both files are in utf8, but the file with texts can be made in any encoding and it is indicated when opening

import os 
import fileinput 

def latinizator(letter, dic): 
  for i, j in dic.items(): 
    letter = letter.replace(i, j) 
  return letter 

legend = { 

'Ё':'Ö', 
'Ж':'Ž', 
'З':'Z', 
'И':'I', 
'Й':'Î', 
'Ч':'Č', 
'Ш':'Š', 
'Щ':'Ś', 
'Ъ':'V', 
'Ы':'Y', 
'Ь':'V', 
'Э':'E', 
'Ю':'Ü', 
'Я':'Ä', 

#Дополнительные знаки 
'ий':'í', 
'ую':'ú', 
'ой':'ó', 
'ей':'é', 
'ая':'á', 
'ть':'ć', 
} 

with open('123.txt', 'r', encoding='utf8') as f: 
  for line in f: 
    print(latinizator(line, legend), end='')

123.txt
Hedgehog
paranoia
=========
ÖŽ
paranoia