Is there a way to stop the __init__ method from executing?

Question

I have a class Point. Its __init__ method checks if there is a point on turtle canvas. If it finds that it is there already, I need to prevent the init from any further execution.

points = []
class Point():
    def __init__(self, pen, points=points):
        self.x = pen.xcor()
        self.y = pen.ycor()
        for point in points:
            if point == (self.x, self.y, pen):
            # here, I need to stop __init__ from executing
            return True# this raises an error, but does not stop
            #the function the way I want
        points.append((self.x, self.y, pen))
        self.pen = pen
        self.get()

point1 = Point(p)

Here's what I get:

Traceback (most recent call last):
  File "<pyshell#2>", line 1, in <module>
    point1 = Point(p)
TypeError: __init__() should return None, not 'bool'

Answer 1

As the error message states, __init__() should return None, not 'bool'. Change return True to a bare return (which is equivalent to return None).

for point in points:
    if point == (self.x, self.y, pen):
        return

---

Its __init__ method checks if there is a point on turtle canvas. If it finds that it is there already, I need to prevent the init from any further execution.

That said, the difficulty you're having is indicative of a design flaw. A point shouldn't check an external list of points and refuse to be constructed; rather, the code that's creating the point should do the check.

I would hoist the loop out of the constructor and have the caller do the check.