Walter Dörwald wrote:
M.-A. Lemburg wrote:
Walter Dörwald wrote:
Let's compare example uses:
1) Having feed() as part of the StreamReader API: --- s = u"???".encode("utf-8") r = codecs.getreader("utf-8")() for c in s: print r.feed(c) ---
I consider adding a .feed() method to the stream codec bad design. .feed() is something you do on a stream, not a codec.
I don't care about the name, we can call it stateful_decode_byte_chunk() or whatever. (In fact I'd prefer to call it decode(), but that name is already taken by another method. Of course we could always rename decode() to _internal_decode() like Martin suggested.)
It's not that name that doesn't fit, it's the fact that you are mixing a stream action into a codec which I'd rather see well separated.
2) Explicitely using a queue object: --- from whatever import StreamQueue
s = u"???".encode("utf-8") q = StreamQueue() r = codecs.getreader("utf-8")(q) for c in s: q.write(c) print r.read() ---
This is probably how an advanced codec writer would use the APIs to build new stream interfaces.
3) Using a special wrapper that implicitely creates a queue: ---- from whatever import StreamQueueWrapper s = u"???".encode("utf-8") r = StreamQueueWrapper(codecs.getreader("utf-8")) for c in s: print r.feed(c) ----
This could be turned into something more straight forward, e.g.
from codecs import EncodedStream
# Load data s = u"???".encode("utf-8")
# Write to encoded stream (one byte at a time) and print # the read output q = EncodedStream(input_encoding="utf-8", output_encoding="unicode")
This is confusing, because there is no encoding named "unicode". This should probably read:
q = EncodedQueue(encoding="utf-8", errors="strict")
Fine. I was thinking of something similar to EncodedFile() which also has two separate encodings, one for the file side of things and one for the Python side.
for c in s: q.write(c) print q.read()
# Make sure we have processed all data: if q.has_pending_data(): raise ValueError, 'data truncated'
This should be the job of the error callback, the last part should probably be:
for c in s: q.write(c) print q.read() print q.read(final=True)
Ok; both methods have their use cases. (You seem to be obsessed with this final argument ;-)
I very much prefer option 1).
I prefer the above example because it's easy to read and makes things explicit.
"If the implementation is hard to explain, it's a bad idea."
The user usually doesn't care about the implementation, only it's interfaces.
Bye, Walter Dörwald
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