Hi Salvatore,

on_enter is expecting a function object, but you’ve passed the result of a function call. Here’s what it should look like:

def cable(extents):
   print(extents)

rect_tool = RectangleTool(ax,on_enter=cable)

Once you get it working, we’d love for you to submit a Pull Request with an example in the docstring for RectangleTool.

Regards,

Steve