How to replace Python 3.4.3 by 3.5

Im on Ubuntun 17.2 and I have Python version 3.4.3 installed. However for a package to install I need Python 3.5. Trying to simply use the apt-get routine only that python3 is up to date. Trying to directly specify the version of python via

sudo apt-get install python3=3.5

only tells me that the version does not exist. Can anyone help?

Edit: Adding the repository mentioned in the comments allowed me to install python3.5. However the package still will not install.The package that I want to install is called kwant. I try installing it by cloning into git:

sudo pip3 install git+https://gitlab.kwant-project.org/kwant/kwant.git

However I still get the error

Error: Python 3.5 required, but 3.4.3 is installed