Python subtracting floats

I have the following code embeded in a class.Whenever I run distToPoint it gives the error 'unsupported operand type(s) for -: 'NoneType' and 'f开发者_JAVA技巧loat'' I don't know why it's returning with NoneType and how do I get the subtraction to work?

Both self and p are supposed to be pairs.

def __init__(self, x, y):
    self.x = float(x)
    self.y = float(y)
def distToPoint(self,p):
    self.ax = self.x - p.x
    self.ay = self.y - p.y
    self.ac = math.sqrt(pow(self.ax,2)+pow(self.ay,2)) 

For sake of comparison,

import math

class Point(object):
    def __init__(self, x, y):
        self.x = x + 0.
        self.y = y + 0.

    def distToPoint(self, p):
        dx = self.x - p.x
        dy = self.y - p.y
        return math.sqrt(dx*dx + dy*dy)

a = Point(0, 0)
b = Point(3, 4)

print a.distToPoint(b)

returns

5.0

You should check what value of p you are sending to the function, so that it has an x and y that are floats.

Old post (on second thought, I don't think you were trying to use distToPoint this way):

distToPoint doesn't return a value, this is probably the problem.