I always install Python on my computer, it is too useful to be without. Usually I will install the latest Python 2 followed by the latest Python 3. Currently this is Python 2.7.x and Python 3.4.x. It should be noted that Python 2.7.x is the last Python 2 branch, there will not be a Python 2.8.x, current focus is on Python 3.5.x and onwards.
There are both 32-bit and 64-bit versions of Python available and if both are installed and have the same Python version number then the 64-bit version will launch as this is "preferred". However I normally install just the 32-bit as this is seem to be the more compatible with external libraries but I don't believe it is a big issue.
If you install, like I have Python 2.7.x and Python 3.4.x on the same machine then executing py on the command line will cause the launcher to start the Python 2.7 python.exe, however if you specify py -3 then you will get Python3.4, which is nice. It is this launcher that also makes the 32/64 bit decision.
There is more information on all the above at 3. Using Python on Windows — Python 3.4.2 documentation which also includes documentation on "shebang" lines, which Python now respects on Windows as well as Linux.
It is worth noting that with Python 3.7.2 work is ongoing to get Python into the Microsoft Store, for very easy installation, however it does have limitations, so see 3. Using Python on Windows — Python 3.7.2 documentation for details.