Using Methods in a Defined Class

Question

I am trying to make a script in which I am supposed to make a class Dot, which takes a X position, a Y position, and Color. I have made the class and all of the methods to go with it. The problem I am running into is how to apply the method. Here is what I have done:

class Dot:
    '''A class that stores information about a dot on a flat grid
       attributes: X (int) Y (int), C (str)'''

    def __init__(self, xposition, yposition, color):
        '''xposition represents the x cooridinate, yposition represents
           y coordinate and color represent the color of the dot'''
        self.X = xposition
        self.Y = yposition
        self.C = color


    def __str__(self):
        "Creates a string for appropiate display to represent a point"
        return str(self.X) + " " + str(self.Y) + " " + str(self.C)

    def move_up(self,number):
        '''Takes an integer and modifies the point by adding the given
           number to the x-coordinate
           attributes: number (int)'''

        self.Y = number + self.Y

    def move_right(self,number):
        '''Takes an integer and modifies the Point by adding the given number to the y-coordinate
           attributes: number (int)'''

        self.X = number + self.X

    def distance_to(point2):
        '''Takes another Dot and returns the distance to that second Dot
           attributes: X (int) Y (int)'''

        distance = ((self.X - point2.X )**2) + ((self.Y - point2.Y)**2)
        real_distance = distance.sqrt(2)

        return real_distance



point1 = (2,3,"red")
print("Creates a" + " " + str(point1[2]) + " " + "dot with coordinates (" + str(point1[0]) + "," + str(point1[1]) + ")")
point2 = (1,2,"blue")
print("Creates a" + " " + str(point2[2]) + " " + "dot with coordinates (" + str(point2[0]) + "," + str(point2[1]) + ")")
new_point = point1.move_up(3)
print("Moves point up three on the y axis")

Here is what is returned:

AttributeError: 'tuple' object has no attribute 'move_up'

we're in the same class i think and i got the same problem that you had... did their answers fix the problem? because they didnt fix mine — holaprofesor
– holaprofesor, Commented Apr 1, 2015 at 23:46

Selcuk · Accepted Answer · 2015-04-01 21:07:23Z

3

You never instantiate a Dot object, you create a tuple with 3 elements. Change it to:

point1 = Dot(2,3,"red")
point2 = Dot(1,2,"blue")

and instead of

print("Creates a" + " " + str(point1[2]) + " " + "dot with coordinates (" + str(point1[0]) + "," + str(point1[1]) + ")")

use

print "Creates a" + " " + point1.C + " " + "dot with coordinates (" + str(point1.X) + "," + str(point1.Y) + ")"

By the way, the .format() syntax is much more clear:

print "Creates a {0} dot with coordinates ({1}, {2})".format(point1.C, point1.X, point1.Y)

answered Apr 1, 2015 at 21:07

Selcuk

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1 Comment

Brett Over a year ago

When I change the script to yours, I receive a type error 'Dot' object does not support indexing. Any idea why this is occurring?

DNA · Accepted Answer · 2015-04-01 21:08:02Z

0

Your code:

point1 = (2,3,"red")

does not create an instance of your Dot class - it just creates a tuple.

To create a Dot, you have to call its constructor (__init__), i.e:

point1 = Dot(2,3,"red")

answered Apr 1, 2015 at 21:08

DNA

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