Python-3 and \x Vs \u Vs \U in string encoding and why
Python gives you a representation of the string, and for non-printable characters will use the shortest available escape sequence.
\x80 is the same character as \u0080 or \U00000080, but \x80 is just shorter. For chr(57344) the shortest notation is \ue000, you can't express the same character with \xhh, that notation only can be used for characters up to \0xFF.
For some characters there are even single-letter escapes, like \n for a newline, or \t for a tab.
Python has multiple notation options for historical and practical reasons. In a byte string you can only create bytes in the range 0 - 255, so there \xhh is helpful and more concise than having to use \U000hhhhh everywhere when you can't even use the full range available to that notation, and \xhh and \n and related codes are familiar to programmers from other languages.