Many have chimed in on this topic but I thought I would lend my stance--for whatever it is worth.

I also believe most of these do not fit concept of a character codec and some sort of transforms would likely be useful, however most are sort of specialized (e.g., there should probably be a generalized compression library interface al la hashlib):

rot13: a (albeit simplistic) text cipher (str to str; though bytes to bytes could be argued since since many crypto functions do that)

zlib, bz2, etc. (lzma/xz should also be here): all bytes to bytes compression transforms

hex(adecimal) uu, base64, etc.: these more or less fit the description of a character codec as they map between bytes and str, however, I am not sure they are really the same thing as these are basically doing a radix transformation to character symbols and the mapping it not strictly from bytes to a single character and back as a true character codec seems to imply. As evidenced by by int() format() and bytes.fromhex(), float.hex(), float.fromhex(), etc., these are more generalized conversions for serializing strings of bits into a textual representation (possibly for human consumption).

I personally feel any <type/class>.hex(), etc. method would be better off as a format() style formatter if they are to exist in such a space at all (i.e., not some more generalized conversion library--which we have but since 3.x could probably use to be updated and cleaned up).