The magic module can be used to determine a files encoding, such as us-ascii or utf-8. To use the magic module, you will need to install the python-magic packages.

pip install python-magic

Then do something like this to return the encoding.

#!/usr/bin/python3
import magic

blob = open('/path/to/exampe.txt', 'rb').read()
m = magic.open(magic.MAGIC_MIME_ENCODING)
m.load()
encoding = m.buffer(blob)

print(f"example.txt encoding = {encoding}")

Which should return something like this.

example.txt encoding = utf-8