[Tutor] canvas -> CLASSES

[Teresa Stanton]

CLASSES: This is where I start getting confused.  I've re-written the maze, 
per the guidance of John Fouhy (by the way, pretty cool!).  Wish I had 
thought of doing it that way to begin with, lol.  In any case, I'm trying to 
put it into a class, and for some reason it all starts to get jumbled here, 
which it shouldn't because I write in C++.  None-the-less, I'm having some 
issues.  I've attached the changes I've made, which worked before I started 
putting it in a class.  I still need to work on the pathways, but figured I 
would get this into a class format before I go any further.

Since I've put it in a class, my design is off because I don't know how to 
'call' it, among other issues.  Do the point definitions of the walls, boxes 
and T's get put inside the function?  They could also be a file, but I don't 
think that would be necessary.  Right now the function calls itself and I 
don't think its the best way to do it, mostly because I don't know what to 
pass it to begin with.  Can someone please just stop my mind from going 
different directions?  Well, perhaps not, but point me in the right 
direction?

Thanks

T

----- Original Message ----- 
From: "John Fouhy" <john at fouhy.net>
To: "Python Tutor" <tutor at python.org>
Sent: Monday, May 07, 2007 3:22 PM
Subject: Re: [Tutor] canvas -> make an object 'seem' to move


> On 08/05/07, Teresa Stanton <tms43 at clearwire.net> wrote:
>> I seem to be stuck again.  I've attached my entire file (and the .gif I'm
>> using.  My son made this .gif, its our lab). The problem is my xp (the
>> variable I use for my x coordinate) isn't updating after the .gif moves. 
>> I
>> think I should probably organize the entire module better, but then 
>> again,
>> I've never written anything this big in Python, and nothing like this in
>> Tkinter.  So, perhaps someone will have a suggestion?
>
> Some general comments:
>
> """
> #This will build the north (top) wall of the maze
> canvasOne.create_line(10, 10, 790, 10, width = 3, fill = 'blue') #west to 
> east
> canvasOne.create_line(20, 20, 395, 20, width = 3, fill = 'blue') #2nd
> line, west to middle
> canvasOne.create_line(395, 20, 395, 100, width = 3, fill = 'blue')
> #middle to south
> canvasOne.create_line(405, 20, 405, 100, width = 3, fill = 'blue')#2nd
> middle to south
> canvasOne.create_line(395, 100, 405, 100, width = 3, fill = 'blue')
> #short west to east
> canvasOne.create_line(405, 20, 780, 20, width = 3, fill = 'blue') #2nd
> line cont, middle to east
> """
>
> This would be a good opportunity to define some functions.  eg, you
> could do this:
>
> canvasOne = Canvas(width = 800, height = 700, bg = 'black')
> canvasOne.pack()
>
> def createWall((x0, y0), (x1, y1), colour='blue', width=3):
>    """ Create a wall from (x0, y0) to (x1, y1). """
>    canvasOne.create_line(x0, y0, x1, y1, width=width, fill=colour)
>
> Then ... hmm, I see from running your code that your lines are all
> effectively continuous.  So you could represent each wall by a series
> of points.  eg:
>
> outerWall = [(10,10), (790,10), (790, 360), ...] # etc
> innerWall1 = [...]
> # etc
>
> walls = [outerWall, innerWall1, ...]
>
> Then you could draw them like:
>
> for wall in walls:
>    for i in range(len(wall-1)):
>        createWallall(outerWall[i], outerWall[i+1])
>
> Second comment:
>
> """
> xp = 100
> yp = 600
>
> # ...
>
> #onClick Vertical moves the .gif based on where the mouse is clicked
> #newY is new location for yp
> def onClickVertical(newY, xp, yp):
>    print 'here'
>    for i in range(newY):
>        yp += .8
>        canvasOne.coords(ph, xp, yp)
>        time.sleep(.001)
>        canvasOne.update()
>    return xp, yp
> """
>
> I notice you have a statement:
>
>    yp += .8
>
> in this function.  Are you aware that this will _not_ change the value
> of yp outside the scope of the function?
>
> If you want to change yp in the global scope, you need to tell python
> to treat it as a global variable, by putting the statement 'global yp'
> near the top of that function.
>
> A better course of action (global variables are a bit ugly) might be
> to encapsulate your maze into a class.  eg:
>
> class Maze(object):
>    def __init__(self):
>        # initial position of actor
>        self.xp = 100
>        self.yp = 600
>        # create maze, etc.
>
>    def onClickVertical(self, newY, xp, yp):
>        # etc
>
> HTH!
>
> -- 
> John.
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
>
> 
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