how to install opencv for python3.7 when default python3 is python3.5

I am trying to install opencv for my JetsonTX1. I have to build OpenCV from source CMake follow the link https://www.jetsonhacks.com/2018/06/04/build-opencv-3-4-with-cuda-on-nvidia-jetson-tx1/The issue is Jetson has python 3.5 as default Python. I would like to update to python3.7. I used update-alternatives to switch python3 point to python3.7. But when I build the opencv with CMake, it still choose python3 interpreter as Python 3.5. Is there a way to force install opencv for python3.7?