我在脚本中先前定义的函数的名称错误

Question

I'm building a Rectangle Class to see if two rectangles are touching at the corners. It's the last exercise by the openbookproject for python chapter 16. http://openbookproject.net/thinkcs/python/english3e/classes_and_objects_II.html

The problem I'm having is that I've defined a function same_coordinates and then used that function to define a method corner_touching however when I do this I get a NameError: name 'same_coordinates' is not defined and I'm not sure why.

class Rectangle:
"A class to manufacture Rectangle objects"
...
   def same_coordinates(P1,P2):
       return P1.x == P2.x and P1.y == P2.y

   def corner_touching(self,r2):
       r1bl = cao.Point(self.corner.x,self.corner.y)
       r1br = cao.Point(self.corner.x+self.width,self.corner.y)
       r1tr = cao.Point(self.corner.x+self.width,self.corner.y + 
       self.height)
       r1tl = cao.Point(self.corner.x,self.corner.y + self.height)

       r2bl = cao.Point(r2.corner.x,r2.corner.y)
       r2br = cao.Point(r2.corner.x+r2.width,r2.corner.y)
       r2tr = cao.Point(r2.corner.x+r2.width,r2.corner.y + r2.height)
       r2tl = cao.Point(r2.corner.x,r2.corner.y + r2.height)

    return same_coordinates(r1bl,r2tr) or same_coordinates(r1tl,r2br) or \
         same_coordinates(r1tr,r2bl) or same_coordinates(r1br,r2tl)

I've use "..." to represent the init and other methods which work fine. The error I get when I use two rectangle is:

Exception has occurred: NameError name 'same_coordinates' is not defined

which is funny because I swear I've defined it two lines above corner_touching. Any help would be greatly appreciated!!!

Answer 1

If intersection for method same_coordinates is like above then this is a class method, and you should call it on an object. If you move this method outside of class it should work.

Answer 2

What you can try is doing this:

return self.same_coordinates(r1bl,r2tr) or self.same_coordinates(r1tl,r2br) or \
     self.same_coordinates(r1tr,r2bl) or self.same_coordinates(r1br,r2tl)

The thing is that you have self in the function. In the class use self.FUNC to call it. I hope it works!

Answer 3

same_coordinates is an attribute of the Rectangle class, not a variable in any local or global scope. You need to access it via Rectangle or one of its instances.

def corner_touching(self,r2):
    # ...

    return self.same_coordinates(r1bl, r2tr) or \
           self.same_coordinates(r1tl, r2br) or \
           self.same_coordinates(r1tr, r2bl) or \
           self.same_coordinates(r1br, r2tl)

Since it is an attribute, it should also be declared as a static method, since it takes two Point instances--but no Rectangle instance--as arguments:

@staticmethod
def same_coordinates(P1,P2):
    return P1.x == P2.x and P1.y == P2.y

---

Or, you can define it as a global function, in which case you won't need to change corner_touching :

def same_coordinates(P1, P2):
    return P1.x == P2.x and P1.y == P2.y


class Rectangle:
    "A class to manufacture Rectangle objects"

   def corner_touching(self,r2):
       # ...

       return same_coordinates(r1bl, r2tr) or \
              same_coordinates(r1tl, r2br) or \
              same_coordinates(r1tr, r2bl) or \
              same_coordinates(r1br, r2tl)

Answer 4

Use __eq__ magic methods. What you are trying to do is exactly what __eq__ does.

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __eq__(self, other):
        return self.x == other.x and self.y == other.y

p1 = Point(3, 4)
p2 = Point(4, 4)
p3 = Point(3, 4)
print(p1 == p2) # will print False
print(p1 == p3) # will print True