Why do I have to install PyTorch separately?

If you install 3LC in an environment without PyTorch and attempt to import the tlc-package you will get an exception complaining that TorchVision needs to be installed:

3LC requires torchvision to be installed. A suitable version can be installed with:
        pip install tlc[torch]
        or be found at https://pytorch.org/

The reason 3LC does not depend on torch (and thus doesn’t automatically install it) is that PyTorch is available in several versions targeting different compute platforms. Most users will likely have already installed their preferred version of torch, and we do not want to modify their environment.

However, if a user does not have a preference for a specific version of torch, a default version will be provided by executing pip install tlc[torch] after the installation of 3LC.