Tkinter: getting coordinates of a mouse drawn rectangle

Working on the answer of my previous question, I wonder how to get the coordinates of the 4 pixels representing the corners of the rectangle as well as its 2 dimensions ?

Answer

You can use canvas.bbox(item) to get the coordinates of the bounding box of an item on the canvas. Because your item is a rectangle, the bounding box exactly represents the rectangle.
In your case it would be:

self.canvas.bbox(self.rect)

This returns a tuple containing (x0, y0, x1, y1) in which point 0 is the upper left corner and point 1 is the lower right corner.
You can easily convert these to the four corners and sizes:

Upper left  = x0, y0
Upper right = x1, y0
Lower left  = x0, y1
Lower right = x1, y1

width  = x1-x0
height = y1-y0