avoiding python@2 redundant dependency I installed gdal using homedal because I need it for ortho4xp, which uses python3. I noticed that gdal depends on  both python and python@2. Gdal is not the only package doing this. It pulls in numpy, which also specifies both python versions as a dependency. It seems there are lots of packages still requiring python@2

I'm assuming there's a reason for packages requiring both versions of python but I was wondering if there are ways of avoiding having to have python2 around?
There is no getting around the pain of managing dependencies. What you are seeing is that for many, many years python 2 was the standard and as we finally are reaching the end of support, some major frameworks are making the move after preparing for years to do so.  For the next 6 months, I would expect most active or easy to port projects to move to python 3. Time will tell of course. 

If you feel you want or need to force your transition to python 3 in homebrew, I would try first removing it so you can validate you actually need it.

brew rm python@2


If you do have it as a dependency, you probably can do nothing and just give up a little space and a little time as every package you care about gets updated to use python 3. Set your path to use the version you want and just let it fade into history.