Can installing Python 3 wrong break other codes, applications etc. in Mac; or can I just install how I want? Cause I code in Python 3 and my Mac's built-in is 2.7
(By "how i want", I mean can any method work without any problem)
You can simply install a Python3 version. If you use Homebrew you can easy install a version with the following command:
brew install python3
After the installation you can check your currently python version:
python3 --version
At the end you can still run python scripts with Python2 by simply typing python.