Method that calculates deviation in Python

Question

I am trying to learn object oriented programming in Python. To do this, I need to create a method that calculates the slope of the line connecting the origin to the point. (I think), we assume that the origin is (0,0). For instance:

Point(4, 10).slopeFromOrigin()
2.5
Point(12, -3).slopeFromOrigin()
-0.25
Point(-6, 0).slopeFromOrigin()
0

And we use the equation slope = (Y2 - Y1) / (X2 - X1)to calculate the slope. In addition, since division by 0 is not allowed, we need to return Nonewhen the method completed with an error. Here is what I tried:

class Point:

#Point class for representing and manipulating x,y coordinates

    def __init__(self, initX, initY):

#Create a new point at the given coordinates

        self.x = initX
        self.y = initY

    def getX(self):
        return self.x

    def getY(self):
        return self.y

    def distanceFromOrigin(self):
        return ((self.x ** 2) + (self.y ** 2)) ** 0.5

#define a method called slopeFromOrigin here

    def slopeFromOrigin(self):

#set origin values for x and y (0,0)

        self.x = 0
        self.y = 0

#slope = (Y2 - Y1) / (X2 - X1)

        if (Point(x) - self.x) == 0:

            return None

        else: 

            return (Point(y) - self.y) / (Point(x) - self.x) 

#some tests to check our code

from test import testEqual
testEqual( Point(4, 10).slopeFromOrigin(), 2.5 )
testEqual( Point(5, 10).slopeFromOrigin(), 2 )
testEqual( Point(0, 10).slopeFromOrigin(), None )
testEqual( Point(20, 10).slopeFromOrigin(), 0.5 )
testEqual( Point(20, 20).slopeFromOrigin(), 1 )
testEqual( Point(4, -10).slopeFromOrigin(), -2.5 )
testEqual( Point(-4, -10).slopeFromOrigin(), 2.5 )
testEqual( Point(-6, 0).slopeFromOrigin(), 0 )

As you can see, I'm trying to say that we need the first Point parameter for x2, and the second Point parameter - y2. I tried it like this and got it

NameError: name 'y' is not defined on line 32.

I also tried to get the Point index values ​​as follows:

return (Point[0] - self.y / (Point[1] - self.x)

But it also gave me an error message:

TypeError: 'Point' does not support indexing on line 32

, x y Point, , . , , . .

Answer 1

self.x = 0
self.y = 0

. . 0...

Point(x) Point(y) - , self.x self.y.

" ". , None, self.x == 0.

,

def slopeFromOrigin(self):
    if self.x == 0:
        return None
    return self.y / self.x

def slopeFromOrigin(self):
    return None if self.x == 0 else self.y / self.x

Python None

def slopeFromOrigin(self):
    if self.x != 0:
        return self.y / self.x

---

, , , - "". ,

origin = Point(0,0)
Point(-6, 0).slopeFromPoint(origin)

Answer 2

        if (Point(x) - self.x) == 0:

        return None

    else: 

        return (Point(y) - self.y) / (Point(x) - self.x) 

, , Point x2, Point - y2.

NameError: 'y' 32.

y, , .

Point :

return ( [0] - self.y/( [1] - self.x)

:

• "" - , ( ).

• , Point . variableName[index], variableName __getitem__(self, key). :

  >>> class GoodListClass:
  ...     def __init__(self, list):
  ...         self.myList = list
  ...     def __getitem__(self, key):
  ...         return self.myList[key]
  ...
  >>> class BadListClass:
  ...     def __init__(self, list):
  ...         self.myList = list
  ...
  >>> someList = range(10)
  >>> goodListObject = GoodListClass(someList)
  >>> badListObject = BadListClass(someList)
  >>> print(goodListObject[2])
  2
  >>> print(badListObject[2])
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  AttributeError: BadListClass instance has no attribute '__getitem__'