> But if I add options for controlling the compression level, I would add options -1 ... -9. I never used verbose forms --fast and --best.

If we add options, I would prefer to only add --fast and --best which are easy to understand. I really have no idea of the difference between -3 and -4 for example. In practice, I don't think that anyone uses these -N options on the common line.

To be honest, I never passed any option to gzip: I always use "gzip file" to get "file.gz". I don't really care of it's file. I just hope that it's smaller :-)

But I'm not against add --best and --fast. By the way, on Linux, gzip default compression level is 6 whereas Python uses 9 by default. I agree to make Python more consistent with Unix tools. In that case, again, it makes sense to add an option to get again --best (level 9).