On Sun, 07 May 2006 10:36:00 -0400, Ken Tilton <[EMAIL PROTECTED]>
wrote:
>[...]
>
>Your spreadsheet does not have slots ruled by functions, it has one slot
>for a dictionary where you store names and values/formulas.
>
>Go back to your example and arrange it so a and b are actual slots (data
>members? fields?) of the spreadsheet class. You can just stuff numbers in a:
>
> sheet1.a = 42
>
>but b should be somehow associated with a rule when sheet1 is created.
>As I said in the other post, also associate an on-change callback with
>slots a and b.
I must be missing something - seems this should be easy using
__setattr__ and __getattr__. Then _literally_ there's just a
dict containing names and functions, but when you _use_ the
class it looks just like the above:
>[...]
>
>When that is done we can look at a working example and see how well
>Python fared without macros and full-blown lambda.
No lambda in the non-programmer-half-hour implementation below.
You need to define a named function for each cell to use as
a callback. Except for that what are Cells supposed to do that
the implementation below doesn't do?
"""PyCells.py"""
class Cell:
def __init__(self, name, owner, callback):
self.name = name
self.callback = callback
self.owner = owner
def onchange(self, value):
self.value = value
self.callback(self, value)
class Cells:
def __init__(self):
#self.slots = {}
#Oops, don't work so well with __setattr__:
self.__dict__['slots'] = {}
def __setattr__(self, name, value):
self.slots[name].onchange(value)
def __getattr__(self, name):
return self.slots[name].value
def AddCell(self, name, callback):
self.slots[name] = Cell(name, self, callback)
***********
Sample use:
cells = Cells()
def acall(cell, value):
cell.owner.slots['b'].value = value + 1
cells.AddCell('a',acall)
def bcall(cell, value):
cell.owner.slots['a'].value = value - 1
cells.AddCell('b',bcall)
cells.a = 42
print cells.a, cells.b
cells.b = 24
print cells.a, cells.b
************************
David C. Ullrich
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