Since Python 3.2.2 (I don't have earlier version to test with),

>>> "\udc80".encode("utf-8")
UnicodeEncodeError: *utf-8* codec can't encode character '\udc80'...

but

>>> b"\xff".decode("utf-8")
UnicodeDecodeError: *utf8* codec can't decode byte 0xff in position 0

and the table on the documentation of the codec module suggests *utf_8* as the name of the codec, which I believe to be equivalent to "utf_8" because '-' is not a valid character of an identifier.

Can we at least make the above two consistent? I would go for "utf-8", which was probably introduced for rejecting surrogates, but "utf8" has been there for years. What do we do? I am happy to submit patches for all branches. These are one-liners anyway.

The backward compatibility risk should be pretty low as usually you don't get encoding from these errors and I don't see any use of PyUnicode(Encode|Decode)Error_GetEncoding in trunk, although I'm using it for issue #12892. 

Also, "latin_1" displays as *latin-1* but "iso2022-jp" displays as *iso2022_jp*. I care less about this nit though.