Is it possible to write on s3 key using boto?
There is no way to append to or modify an existing object in S3.  You can overwrite it completely with new content and you can have versioning enabled on the bucket so the previous versions of the object are still accessible but modifying an existing object is just not supported by the S3 service or API.
I have an app built with boto that sync files locally using librsync(wrapped in a python module). I was wondering if is it possible to write on S3 keys so that I could use librsync remotely, for example I would sync a local file with a file in S3 by taking signatures,delta and patch the result. In the boto documentation it says the open_write is not implemented yet. But I do know the folks like dropbox use s3 and librsync too,so there must be a way...Thanks.