You can use online Python (always an Internet connection is needed):
- online Python 3 (recommended if you don't know what to choose)
- online Python 3 with turtle
- Online Python 2
Or, you can install Python on a Windows computer (you can run Python code without Internet):
- Thonny (Python IDE for beginners) - easy and simple, Python 2 or 3 (recommended)
- Pythonxy (If you want to use pygame module or opencv computer vision module)
Mac and Linux already have Python installed!