Martin v. Löwis wrote:
Nicholas Bastin wrote:
It would be nice if you could optionally specify that the codec would assume UTF-16BE if no BOM was present, and not raise UnicodeError in that case, which would preserve the current behaviour as well as allow users' to ask for behaviour which conforms to the standard.
Alternatively, the UTF-16BE codec could support the BOM, and do UTF-16LE if the "other" BOM is found.
That would violate the Unicode standard - the BOM character for UTF-16-LE and -BE must be interpreted as ZWNBSP.
This would also support your usecase, and in a better way. The Unicode assertion that UTF-16 is BE by default is void these days - there is *always* a higher layer protocol, and it more often than not specifies (perhaps not in English words, but only in the source code of the generator) that the default should by LE.
I've checked the various versions of the Unicode standard docs: it seems that the quote you have was silently introduced between 3.0 and 4.0.
Python currently uses version 3.2.0 of the standard and I don't think enough people are aware of the change in the standard to make a case for dropping the exception raising in the case of a UTF-16 finding a stream without a BOM mark.
By the time we switch to 4.1 or later, we can then make the change in the native UTF-16 codec as you requested.
Personally, I think that the Unicode consortium should not have introduced a default for the UTF-16 encoding byte order. Using big endian as default in a world where most Unicode data is created on little endian machines is not very realistic either.
Note that the UTF-16 codec starts reading data in the machines native byte order and then learns a possibly different byte order by looking for BOMs.
Implementing a codec which implements the 4.0 behavior is easy, though.