Using pre-built Python class and methods within my class-CodePudding

I am trying to understand how Python implements OO. I’m trying to understand how I can use an existing class within my class – so as much of the processing is hidden as possible from the programmer. The exercise I have created is to write a Class Rect that can be used to create an object that has two attributes : len and wid and (somehow) will “contain” another object – which I will call “stylus”. My idea is when I instantiate an object of class Rect, I will pass the length and width of the rectangle and a “stylus” created by

stylus = turtle.Turtle()

Say the Rect object created is rect_obj, then I want to define a method, draw_rect, in Rect that will draw the rectangle. My code attempt is below (*) (which of course doesn’t work).

(*)

class Rect:
    def __init__(self,rect_len,rect_wid,stylus_in):
        self.len = rect_len
        self.wid = rect_wid
        self.stylus = stylus_in

    #
    def draw_rect(self,stylus):

        self.stylus.forward(len)
        self.stylus.right(90)

    # class Square(Rect):
    def __init__(self,side_len):
        self.len =  side_len
        self.wid =  side_len
    import turtle stylus = turtle.Turtle() 

rect_obj = Rect(int(5),int(4),stylus)  

stylus = turtle.Turtle() 

print(rect_obj.len)  


print(rect_obj.wid)  

rect_obj.draw_rect(stylus)

I’m trying to understand how I code the Python so I hide this processing and all that needs to be written is something like:

rect_obj.draw_rect(stylus)

Now, when I run my code it fails in turtle.py with following error messages:

*** Remote Interpreter Reinitialized *** 5 4 Traceback (most recent call last):   File "C:\Users\Clive\Desktop\temp_OOP_turtle.py", line
27, in <module>
    rect_obj.draw_rect(stylus)   File "C:\Users\Clive\Desktop\temp_OOP_turtle.py", line 12, in draw_rect
    self.stylus.forward(len)   File "C:\Users\Clive\AppData\Local\Programs\Python\Python37\lib\turtle.py",
line 1637, in forward
    self._go(distance)   File "C:\Users\Clive\AppData\Local\Programs\Python\Python37\lib\turtle.py",
line 1604, in _go
    ende = self._position   self._orient * distance   File "C:\Users\Clive\AppData\Local\Programs\Python\Python37\lib\turtle.py",
line 257, in __mul__
    return Vec2D(self[0]*other, self[1]*other) TypeError: unsupported operand type(s) for *: 'float' and 'builtin_function_or_method'

Is there anyway I can fix my Python so the code for moving the turtle is provided in a method inside Rect class?

I can get my stylus to draw a rectangle if I put the code currently in draw_rect at the “level” of my main routine (see end **) but that doesn't hide the code that draws the rectangle.

(**) Code that will draw a 50 x 70 rectangle but outside the class Rect: import turtle

smart = turtle.Turtle()
for i in range(2):
    smart.forward(50)
    smart.right(90)
    smart.forward(70)
    smart.right(90)

CodePudding user response：

Answer from comment by @topsail:

in draw_rect you have this mistake: self.stylus.forward(len) should be self.stylus.forward(self.len)