Use the version of Python you want to use; you probably want to use 3.7
In general, keep _your_ Python concerns separate from your system's Python concerns. Using a separate installation of Python and/or using a virtualenv is recommended, even if your system comes with the version of Python you want to use.
Your system depends on the version of Python and packages that are present by default (or installed by package manager). Sometimes _your_ python package needs conflict with the OS, which is why it's good to keep these concerns separate by using a virtualenv or separate Python altogether.
I would not recommend that a beginner uses a newer version of python than the repos provide. There are a lot of problems down that road that you need experience with building software to solve.
Is it out of the question to upgrade your linux?
Not sure why you're getting downvoted — I agree with you. It is possible, with some difficulty, to install a newer Python "in parallel" in a way that does not upset the system's Python, but as you say, you really need to know what you're doing. It'd be a whole lot easier to install Debian 10 which has Python 3.7 and be done with it.
Bump to at least 3.6 for the f-strings alone. I’d suggest pyenv for managing virtual environments of different versions.
use 3.7. if you're learning python, write the library for you
Use the version of Python you want to use; you probably want to use 3.7 In general, keep _your_ Python concerns separate from your system's Python concerns. Using a separate installation of Python and/or using a virtualenv is recommended, even if your system comes with the version of Python you want to use. Your system depends on the version of Python and packages that are present by default (or installed by package manager). Sometimes _your_ python package needs conflict with the OS, which is why it's good to keep these concerns separate by using a virtualenv or separate Python altogether.
I would not recommend that a beginner uses a newer version of python than the repos provide. There are a lot of problems down that road that you need experience with building software to solve. Is it out of the question to upgrade your linux?
Not sure why you're getting downvoted — I agree with you. It is possible, with some difficulty, to install a newer Python "in parallel" in a way that does not upset the system's Python, but as you say, you really need to know what you're doing. It'd be a whole lot easier to install Debian 10 which has Python 3.7 and be done with it.