Question

I have a class Point that accepts position, value and flag as arguments. This class should accept only integers as position and value arguments. I tried the code below, but it doesn’t work properly.

class PointException(Exception):
    pass

class Point():
    def __init__(self, position, value, flag=False):
        try:
            if all([isinstance(x, int) for x in position, value]):
                self.position = position
                self.value = value
                self.point = (position, value)
            self.flag = flag
        except:
            raise PointException("Foo value and position must be integers.")

    def __repr__(self):
        return "< {0}, {1}, {2} >".format(self.position, self.value, self.flag)

    def __eq__(self, other):
        if not isinstance(other, Point):
            return False
        try:
            return all([self.point == other.point, self.flag == other.flag])
        except AttributeError:
            return False

    def __ne__(self, other):
        return not self.__eq__(other)

Update

I get an AttributError when I try Point(1, 1.2), for instance.

AttributeError: Point instance has no attribute 'position'

Answer 1

if all([isinstance(x, int) for x in position, value])

should be

if all(isinstance(x, int) for x in (position, value))

And more generally you have to raise the exception in __init__, not catch it with except:

def __init__(self, position, value, flag=False):
    if not all(isinstance(x, int) for x in (position, value)):
        raise PointException("Foo value and position must be integers.")

    self.position = position
    self.value = value
    self.point = (position, value)
    self.flag = flag

There are other areas of improvement that you can read about in the other answers