Python is included with the Intel's default image for the SD card. So, if you want to run Python scripts, all you have to do is boot from an SD card
If you would like to manipulate the Arduino pins from your Python script, there are two implementations of the Python for Galileo. One, developed by me, tries to keep the Arduino format for manipulating the pins. The second comes from a post made by tony-c on the Intel Maker's forum.
Both of them will allow you to start using the Arduino I/O pins from within your Python scripts.