Python 3.4 and 2.7: Cannot install numpy package for python 3.4

You have not installed the Python 3 development package. Install python3.4-dev:

apt-get install python3.4-dev

The main package never includes the development headers; Debian (and by extension Ubuntu) package policy is to put those into a separate -dev package. To install numpy however, you need these files to be able to compile the extension.

Solved by incrementing the python-dev package until I hit the right one. May need to be incremented further in the future. Poor implementation by python developers.

sudo apt-get install python3.7-dev