Python classes and errors

Working on some homework for a while now and can't seem to figure out how to get around this error. Just to note, I am not allowed to import anything.

The error I am getting I think is due to either my __repr__ or __str__ methods. Here is my code:

class Point: def __init__(self, x = 0, y = 0): """ The constructor allows the user to set values for x and y. Default values are 0. """ self.x = x self.y = y def translate(self, s, t): """ This method translates point x by s and point y by t. """ self.x = self.x + s self.y = self.y + t return self.x, self.y def __str__(self): """ This method returns a string representation of the point. """ return "({0}, {1})".format(self.x, self.y) def __repr__(self): """ This method returns a string representation of the point. """ return "({0}, {1})".format(self.x, self.y) class SimplePoly: def __init__(self, *vertices): """ The constuctor adds all vertices to a list. """ self.vertices = vertices self.pointlist = [self.vertices] def translate(self, s, t): """ This method translates all points of the polygon by (s,t). """ for p in self.pointlist: p.x + s p.y + t print(self.pointlist)

but when I try to do translate to every Point object in the self.pointlist, I get the error:

Traceback (most recent call last): File "<pyshell#170>", line 1, in <module> h.translate(1,1) File "C:/Python34/problem2.py", line 74, in translate p.x + s AttributeError: 'tuple' object has no attribute 'x'

The vertices are Point objects. This is the code I am testing with:

>>> g = Point(2,3) >>> g2 = Point(5,2) >>> g3 = Point(6,7) >>> h = SimplePoly(g,g2,g3) >>> h.translate(1,1)

-------------Problems Reply------------

Your self.pointlist attribute is a list with one tuple in it:

def __init__(self, *vertices):
# ....
self.vertices = vertices
self.pointlist = [self.vertices]

vertices is always a tuple here, which in turn contains your Point() objects. Tuples never have x and y attributes; it is itself not a Point instance.

You may as well replace self.pointlist with self.vertices here. If you needed a mutable sequence, use list() instead of a list literal:

self.pointlist = list(self.vertices)

which creates a list with the elements from the tuple.

Category:python Views:2 Time:2018-04-15

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