In this case, you can only use 'latin1', which directly map one character (\u0000-\u00FF) to/from one byte.

If use 'utf-8', it may map one character to multiple bytes, such as 'Δ' -> b'\xce\x94'

'\x94' is an invalid identifier, it will raise an error:

    >>> '\xce'.isidentifier()   # '\xce' is 'Î'
    True
    >>> '\x94'.isidentifier()
    False

You may close this issue (I can't close it), we can continue the discussion.