[Python-Dev] Dropping bytes "support" in json
Stephen J. Turnbull
stephen at xemacs.org
Fri Apr 10 17:38:03 CEST 2009
Paul Moore writes:
> On the other hand, further down in the document:
> 3. Encoding
> JSON text SHALL be encoded in Unicode. The default encoding is
> Since the first two characters of a JSON text will always be ASCII
> characters [RFC0020], it is possible to determine whether an octet
> stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
> at the pattern of nulls in the first four octets.
> This is at best confused (in my utterly non-expert opinion :-)) as
> Unicode isn't an encoding...
The word "encoding" (by itself) does not have a standard definition
AFAIK. However, since Unicode *is* a "coded character set" (plus a
bunch of hairy usage rules), there's nothing wrong with saying "text
is encoded in Unicode". The RFC 2130 and Unicode TR#17 taxonomies are
annoying verbose and pedantic to say the least.
So what is being said there (in UTR#17 terminology) is
(1) JSON is *text*, that is, a sequence of characters.
(2) The abstract repertoire and coded character set are defined by the
(3) The default transfer encoding syntax is UTF-8.
> That implies that loads can/should also allow bytes as input, applying
> the given algorithm to guess an encoding.
It's not a guess, unless the data stream is corrupt---or nonconforming.
But it should not be the JSON package's responsibility to deal with
corruption or non-conformance (eg, ISO-8859-15-encoded programs).
That's the whole point of specifying the coded character set in the
standard the first place. I think it's a bad idea for any of the core
JSON API to accept or produce bytes in any language that provides a
Unicode string type.
That doesn't mean Python's module shouldn't provide convenience
functions to read and write JSON serialized as UTF-8 (in fact, that
*should* be done, IMO) and/or other UTFs (I'm not so happy about
that). But those who write programs using them should not report bugs
until they've checked out and eliminated the possibility of an
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