I spent about 5 hours trying to install scipy for Python 3, so I wanted to make sure others could find out how to do it.
sudo apt-get install python3-scipy. That should do it.
Things I tried that didn't work how I wanted:
Installing with pip
Installing with pip3
Installing python-scipy with apt-get
Installing miniconda (anaconda was too big) and using miniconda to install sci-py
In short, don't do what I did. Just run
sudo apt-get install python3-scipy. (You may need to update apt-get if it doesn't find python3-scipy right away.)