how should I use the parameter numBubbles in this function?
numBubbles is the number of bubbles you have to create and add to the list.
Therefore, that is the range of the for loop which you create the bubbles.
for numBubbles in range (DEFAULT_BUBBLE_NUM) ?
No, the range should be numBubbles because you will create bubbles for numBubbles times.
So inside the for loop, is it correct to use a function self.circle.draw() to draw bubbles with different positions? Thank you
In the setupBubbles function, you just need to create bubbles and add them to a list. You shouldn't draw them. You will draw them in the main function.
You use numBubble to loop through every bubble you want to create