Can't understand OpenCV Python functions arguments

Question

I'm learning OpenCV and also Python. But I can't understand these funcions parameters:

cv2.Canny(image, threshold1, threshold2[, edges[, apertureSize[, L2gradient]]])

After ther argument "threshold2" I can't understand anymore, what does these [] means? It's a List? It's a silly question, but I really want to understand.

Answer 1

I assume you're familiar with C/C++, I found I could understand them better when I looked at them from point of view a language I already knew. They are parameters with default values. It means that if you do not supply any values for those parameters, they will use the default ones.

In C/C++ terms:

void point(int x = 3, int y = 4); // 3 , 4 are default values

point(1,2); // calls point(1,2)
point(1);   // calls point(1,4)
point();    // calls point(3,4)