Another newbie question

[John Bushnell]

I think that's supposed to be [(i + j) % 2] for the index to the
("green","red") tuple
(since i*8 is always even).

solaris_1234 at yahoo.com wrote:
> Mike,
>
> Thanks for your insight. It has been a big help.
>
> I guess I was trying to learn too much with my original code. Trying to
> implement inheritance, object creation, calling methods via inheritance
> made the code harder than it needed to be.
>
> I'm off to study the code. (Hmm.. how does python parse ("green",
> "red")[(i * 8 + j) % 2]  command ... he says while reaching for "python
> for the semi-illiterate"  ...)
>
> Again, thanks for your help.
>
>
> Jpl
>
>
> Mike Meyer wrote:
> > "solaris_1234" <solaris_1234 at yahoo.com> writes:
> >
> > > 1)  The stmt "board.Blist[10].DrawQueen(board.Blist[10].b1)" seems
> > > awkward. Is there another way (cleaner, more intuitive) to get the
> > > same thing done?
> >
> > Yes. Reaching through objects to do things is usually a bad idea. Some
> > languages don't allow you to do that at all; they require you to
> > provide methods for manipulating the state of the object For instance,
> > you can extend your MyBoard class with an extra method:
> >
> >    def DrawQueen(self, cell):
> >        square = self.Blist[cell]
> >        square.DrawQueen(square.b1)
> >
> >
> > And then those two lines become:
> >
> >     board.DrawQueen(10)
> >     board.DrawQueen(22)
> >
> > Except that's still ugly - you probably want something like
> > board.DrawQueen(1, 2).
> >
> > Basically, Blist should be part of MyBoards implementation, not a
> > visible attribute. You should define methods for MyBoard that let
> > clients manipulate the board, without needing to know how it's
> > represented internally.
> >
> > Along the same lines, why does MyBoard inherit from MyBox? It's not
> > using any of the features of MyBox. The code still works if you don't
> > do that. And why do you pass instances of Cavnas to the methods of
> > MyBox - it's got a canvas already! Do you really expect a MyBox to
> > draw onto Canvases other than it's own (if so, that's a bad design as
> > well).
> >
> > Here's an updated version of your code. I've used the convention of an
> > _ prefix on attributes to indicate implementation details, and made
> > the classes inherit from object, as well as using "box" instead of
> > "b1", and changed the interface to MyBoard squares to use standard
> > 2d-array indexing instead of forcing the clients to do array
> > index calculations. You may have a good reason for doing these things
> > that doesn't appear in your code fragment, but I consider these to be
> > improvements in the fragment.
> >
> > Hmm. "b1" seems to indicate that you will eventually have more than
> > one canvas, which is why you passed in the canvas? In which case, the
> > distinguishing feature would be the number (or mabye the "b1"). In
> > that case, have your clients pass in the number (or name), and look up
> > the canvas in an internal structure.
> >
> >     <mike
> >
> > from Tkinter import *
> > import time
> > totalSolutionCount = 0
> >
> > class MyBox(object):
> >    def __init__(self, myC, myrow, mycolumn, color):
> >       self._box = Canvas(myC, background=color, width=50, height=50)
> >       self._box.grid(row=myrow, column=mycolumn)
> >       self.occupied = False
> >
> >    def ChangebgColor(self):
> >       self._box.config(bg="black")
> >
> >    def DrawQueen(self):
> >       self._box.item = self._box.create_oval(4,4,50,50,fill="black")
> >       self.occupied = True
> >       self._box.update()
> >
> >    def unDrawQueen(self):
> >       self._box.delete(self._box.item)
> >       self.occupied = False
> >       self._box.update()
> >
> > class MyBoard(object) :
> >    def __init__(self, myC):
> >       self._blist = {}
> >       for i in range(8):
> >          for j in range(8):
> >              self._blist[i, j] = MyBox(myContainer, i, j,
> >                                         ("green", "red")[(i * 8 + j) % 2])
> >    def DrawQueen(self, i, j):
> >        square = self._blist[i, j]
> >        square.DrawQueen()
> >
> >    def occupied(self, i, j):
> >        return self._blist[i, j].occupied
> >
> >
> > root=Tk()
> > myContainer = Frame(root)
> > myContainer.pack()
> >
> > board=MyBoard(myContainer)
> >
> > board.DrawQueen(1, 2)
> > board.DrawQueen(2, 6)
> >
> > raw_input()  # A Hack debug statement
> >
> > for i in range(8):
> >     for j in range(8):
> >         if board.occupied(i, j):
> >             print "%d, %d is occupied" % (i, j)
> >
> > raw_input()  # A Hack debug statement
> > print "\n"*3
> >
> >
> >
> >
> > --
> > Mike Meyer <mwm at mired.org>			http://www.mired.org/home/mwm/
> > Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.