I installed pytorch via
conda install pytorch-cpu torchvision-cpu -c pytorch
And I also tried
pip3 install https://download.pytorch
I had the same problem after following the official installation guide in here. I realized that it was my stupid Atom built-in terminal.
Inside the atom terminal, which python returned /usr/bin/python, although it showed the mark of (conda_env)$.
I fixed it by opening a new terminal and activating the (conda_env), and it worked. Verified and which python yields /Users/my_usr/anaconda3/envs/conda_env/bin/python