I've heard how browsers can receive gzipped pages from the server. Can they also gzip form data that they send to the server? And if it's possible, how would I decompress this data on the server?
I'm using AppEngine's webapp module, but a general explanation / pointers to tutorials would be sufficient. I've done some googling to no avail.
I think that browsers probably can send gzipped form data to the server. I don't know if it is common to do so or not.
The sender would need to make sure to have a Content-Encoding: header with a value that included gzip. The body of the message would then need to be encoded with a gzip encoding, and one can compress / decompress gzipped data in python with the gzip.GzipFile class. I don't know if the gzip module is available on appengine -- if it requires a C-module implementation, then it probably wouldn't be (not sure if it does).
As far as the decoding goes, it's possible that the web machinery that runs before your app-engine program gets any input will decode gzipped content. I've done almost no work with appengine, so I'm not familiar with that sort of detail. It's possible though, that you just don't have to worry about it on the server end...it just gets taken care of automatically. You'd have to check.
It might be useful to look at RFC2616, especially the sections for Accept-Encoding and Content-Encoding.
Short answer: No.
See: http://stackoverflow.com/questions/424917/why-cant-browser-send-gzip-request