How does site-packages work with PyTorch and torchvision, given that neither of them get linked to outside their cellars?

[tedmiddleton]

Output of brew config

HOMEBREW_VERSION: 4.4.13
ORIGIN: https://github.com/Homebrew/brew
HEAD: 6ea9df68df4868ce12ea7c51c85b57dce514f2e8
Last commit: 4 days ago
Branch: stable
Core tap JSON: 26 Dec 20:24 UTC
Core cask tap JSON: 26 Dec 20:24 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_EDITOR: nvim
HOMEBREW_MAKE_JOBS: 14
HOMEBREW_NO_AUTO_UPDATE: set
Homebrew Ruby: 3.3.6 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.3.6/bin/ruby
CPU: 14-core 64-bit arm_brava
Clang: 16.0.0 build 1600
Git: 2.39.5 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 15.1-arm64
CLT: 16.2.0.0.1.1733547573
Xcode: 16.2
Rosetta 2: false

Output of brew doctor

Your system is ready to brew.

Description of issue

It's been a while since I've used homebrew python so I'm a bit confused about how this is supposed to work.

Most of the python packages that are available in homebrew seem to contain their own site-packages which then gets linked into the python site-packages directory. But Pytorch's recipe doesn't - it doesn't set up these links into the python site-package dir. Pytorch does have some .pth files, but again it leaves these unlinked inside the cellar.

As a result, torch can't be imported naively, so up until now I've been explicitly adding the PyTorch site-packages directory to my python path in my .bashrc, which is somewhat workable, but actually causes a lot of problems when combined with the (new?) homebrew policy of updating with every brew command - so I've had to also define HOMEBREW_NO_AUTO_UPDATE to avoid having to restart my tmux and my workspace ever time I execute a brew command and accidentally upgrade PyTorch.

Anyways, I installed torchvision and it seems to follow the same policy of not linking out of its cellar, which has me wondering if there's something I'm doing wrong. Am I missing something? Am I supposed to execute some new brew command to make this work properly, without the environment hacks?