raise error

[mcgrim]

I am testing the function __truediv__ in this code, I am specifically interested in the

raise ValueError

command.

Is supposed to raise an error in case the division leads to + or - infinity.

This code instead raises the following error:

Error:
 File "C:/Users/Desktop/python ode/homework22.py", line 53, in <module>
    cc = aa/bb

TypeError: unsupported operand type(s) for /: 'interval' and 'interval'

I am not sure what is wrong, since everything else is working.

---

class interval:
    def __init__(self,left,right):
        self.right=right
        self.left=left
    def __add__(self,other):
        a,b,c,d = self.left, self.right, other.left, other.right
        return interval(a+c,b+d)
    
    def __sub__(self,other):
        a,b,c,d=self.left,self.right,other.left,other.right
        return interval((a-d),(b-c))
    def __mul__(self,other):
        a,b,c,d=self.left,self.right,other.left,other.right
        return interval(min(a*c, a*d, b*c, b*d),
                            max(a*c, a*d, b*c, b*d))
    def __div__(self, other):
        a, b, c, d = self.lo, self.up, other.lo, other.up
        # [c,d] cannot contain zero:
        if c*d <= 0:
            raise ValueError ('Interval %s cannot be denominator because it contains zero' % other)
        return interval(min(a/c, a/d, b/c, b/d),
                            max(a/c, a/d, b/c, b/d))
    def __repr__(self):
        return '[{},{}]'.format(self.left,self.right)

I = interval
aa = I(-3,-2)
bb = I(0,5)
cc = aa/bb
print(aa,bb)       
print(cc)

[buran]

I am testing the function __truediv__ in this code

well, there is no __truediv__() method/function in this code
also, on line 17 you use self.lo, self.up, other.lo, other.up but these attributes are never defined/assigned in your code

[mcgrim]

I left my code untouched with the difference of replacing __div__ with __truediv__,
but now I am getting a different kind of error:

Error:
  File "C:/Users/Desktop/python ode/homework22.py", line 41, in __truediv__
    a, b, c, d = self.lo, self.up, other.lo, other.up

AttributeError: 'interval' object has no attribute 'lo'

I am not sure what you mean by this:

these attributes are never defined/assigned in your code

as I set them as a,b,c,d and I use these characters in my code.
Perhaps I am misunderstanding you.

[buran]

I mean exactly what error says: 'interval' object has no attribute 'lo' (and 'up'). In other words where in the class definition you define attributes lo and up - nowhere.

as I set them as a,b,c,d and I use these characters in my code.

I've noticed that you have wrong understanding of assignment. you don't assign a, b, c and d to self.lo, self.up, other.lo and other.up
what you try is to assign the value of self.lo to a, etc. (this particular assignment is called unpacking, but that is detail - the important is that you [try] to assign the value of self.lo to a) and because there is no attribute interval.lo you get this error

[mcgrim]

I am having an hard time understanding you.

you don't assign a, b, c and d to self.lo, self.up, other.lo and other.up
what you try is to assign the value of self.lo to a

I am trying to assign self.left to a, self.right to b, other.left to c and other.right to d.
is this wrong?

and because there is no attribute interval.lo you get this error

What do you mean?

---

sorry, while replying I think I answered myself, lol !
I got it now, thanks.