'charmap' codec can't decode byte 0x81 in position 45: character maps to code example

Example 1: 'charmap' codec can't decode byte 0x98 in position

file = open(filename, encoding="utf8")

Example 2: UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 92: character maps to

file = open(filename, encoding="cp437")