To save your scripts in the python editor, select save from the menu and your script.py will be saved to your device.
Here is an explanation of the menu items:
Download: This button will download a file with the ".hex" extension that contains the MicroPython interpreter together with your Python script. This is the file you flash onto your micro:bit to run the program.
Load/Save: This will present you with an on-screen dialogue that allows you to select a file to upload to the editor. You can also just drag them from your local filing system and drop them onto the editor window. The online editor will read your MicroPython code from the ".py" file, or it will extract it from the ".hex" file. You can then edit it, and SAVE it or DOWNLOAD it as normal. You can also just download the Python script (without the interpreter) in a file with the ".py" extension. This is a plain text file, so it is the best way to read the code in other editors.
You can load any .hex files generated in any version of MicroPython, and that includes scripts written originally on the microbit.co.uk Python web editor, and scripts written inside the Mu offline editor.
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