Python: refer to instance from event

Let's say I have multiple instances of a sprite object called box. I want each one to be destroyed when the user clicks on it. This is not difficult. I just make the event "On Left Clicked on box" and the action "box: Destroy". But what if I want to use a Python script in the place of the action? "box.Destroy()" doesn't work because it thinks I'm referring to box[0] no matter which box I clicked. So how do I specifically refer to the instance that triggered the event? I'm hoping for a solution that I can apply to any event or action, not just this particular example.

Thanks in advance.

To destroy the first picked "box" Sprite use "SOL":

SOL.box.Destroy()

for obj in SOL.box:
    obj.Destroy()

Thank you, that's perfect. Can you refer me to a more in-depth explanation of the SOL and what goes in it and when?