[Tutor] Confused about __setitem__

[bob gailer]

Jim Hodgen wrote:
> I am learning Python with a  minesweeper-engine project.  Future 
> activities turn my attention to exploring the use of dictionaries as 
> sparse matrices, hence the representation of the gameboard.  
> Why can't I fill the dictionary-as-a-matrix with an instance of class 
> Square?  Why do I need a custom method to make the assignment?  What 
> am I not understanding?
You don't have a sparse matrix here. There is a dictionary entry for 
every square. You might as well use a nested list or an array from one 
of the array modules.

If you want a Baseboard instance to directly accept keyed assignment use:

class Basebaord(dict)

and drop boardsquares.
>
> *_# basics module (mineswobj1)contents..._*
> class Square:
>     mined = True              # False if empty, True if mined, no 
> other values allowed
>     marked = 0                # False if 0, marked-as-mined if 1, 
> marked-as-unknown if 2, no other values allowed
>     displaystate = 0         # covered if 0, marked if 1, exposed if 
> 2, selected if 3, no other values allowed

marked and display state are in conflict and overlap. Consider instead:
    selected = False
    displaystate is one of covered-blank, covered-marked, mined, exposed
>     minedneighbors = 0  # number of mined neighboring squares, max 
> legit value = 8
>  
> class Baseboard:
>     xdimension = 0           # x-dimension of the gameboard, integer 
> value greater than 0
>     ydimension = 0          # y-dimension of the gameboard, integer 
> value greater than 0
>     minenumber = 0        # number of mines on the board for play, 
> value from 0 to (xdimension * ydimension)
>     state = 0                   # playable if 0, not-playable-exploded 
> if 1, not-playable-solved if 2
>     boardsquares = {}   # dictionary used to emulate an addressable 2 
> dimensional grid where an instance of class Square
>                                    # is inserted with a key consisting 
> of a tuple describing its zero-based address in the grid
>
> def initializeboard(xdim, ydim, minenum):
>     gameboard = Baseboard()
>     for yct in range(ydim):
>         for xct in range(xdim):
>             gameboard[(xct,yct)] = Square()
>             print 'gameboard[(',xct,yct, ')] =', gameboard[(xct,yct)]
>
> *_# driver module contents_*
> import basics
>
> mineswobj1.initializeboard(3, 4, 5)
>
> _*#error message*_
> Traceback (most recent call last):
>   File "C:\jmh\Python\minedriver0.py", line 6, in <module>
>     mineswobj1.initializeboard(3, 4, 5)
>   File "C:\jmh\Python\mineswobj1.py", line 26, in initializeboard
>     gameboard[(xct,yct)] = Square()
> AttributeError: Baseboard instance has no attribute '__setitem__'
> ------------------------------------------------------------------------
>
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>   


-- 
Bob Gailer
Chapel Hill NC 
919-636-4239