MicroPython
I have been using Python for some time now. Mostly on my PC and on the Raspberry Pi.
There is a very large support for Python on Windows, Linux, Mac OS-X and other OSses and you will find python modules supporting you in quickly creating an end-user application. This, combined with the fact that you can interactively try some stuff, makes me love Python.
But do keep in mind that Python is a cripting language. This means that most error checking is done in run-time and the execution of your code is not as fast as when compiled in C or C++.
MicroPython is a lean and efficient Python 3 implementation, but there are a few small differences. If you are interested in the differences, check out the http://micropython.org/ website.
There are some board that have MicroPython installed by default, like the boards from pycom, but for other board you may need to install MicroPython yourself.
On these pages I'll give some information on what I did to get things running on my boards.