> Each of the languages above reports the string length as the number of code units that the string occupies. Python 3 strings have (guaranteed-valid) UTF-32 semantics, so the string occupies 5 code units. In UTF-32, each Unicode scalar value occupies one code unit. JavaScript (and Java) strings have (potentially-invalid) UTF-16 semantics, so the string occupies 7 code units. Rust strings are (guaranteed-valid) UTF-8, so the string occupies 17 code units. It is intentional that the phrasing for the Rust case differs from the phrasing for the Python and JavaScript cases. We’ll come to back to that later.

...And the OP is wrong.

1) python doesn't count byte sizes, or UTFxxx stuff. python counts the number of codepoints. Do you want byte-lenght? decode to a byte array and count them. 2) javascript doesn't know about bytes, nor characters, knows only about the fact that "a char is a 16 bit chunk", with a UTF16 encoding. there is no such thing a "code unit with UTF-16 semantics". Similar for java.

oh, and by the way, there are byte sequences that are invalid if decoded from utf-8, so I'm non sure about the "guaranteed-valid" utf-8 rust strings.. (if you want an encoding that can map each byte sequence to a character, there are, like Latin1 and such on, but it's a different matter)