I had numpy installed on the same environment both by pip and by conda, and simply removing and reinstalling either was not enough.
I had to reinstall both.
I don't know why it suddenly happened, but the solution was
pip uninstall numpy
conda uninstall numpy
uninstalling from conda also removed torch and torchvision.
conda install pytorch-cpu torchvision-cpu -c pytorch
pip install numpy
this resolved the issue for me.