On 22 Apr 2005 20:45:55 -0700, "El Pitonero" <[EMAIL PROTECTED]> wrote:
>Bengt Richter wrote: >> I still don't know what you are asking for, but here is a toy, >> ... >> But why not spend some time with the tutorials, so have a few more >cards in your deck >> before you try to play for real? ;-) > >Communication problem. Indeed. > >All he wanted is automatic evaluation a la spreadsheet application. >Just like in Microsoft Excel. That's all. > >There are many ways for implementing the requested feature. Here are >two: > >(1) Push model: use event listeners. Register dependent quantities as >event listeners of independent quantities. When an independent quantity >is modified, fire off the event and update the dependent quantities. >Excel uses the push model. This is essentially what I was demonstrating with the namespace of FunArray, showing object attribute namespace access as perhaps _the_ 'listening" hook of Python -- which properties and overriding base class methods with subclass methods etc. etc. all depend on. FunArray 'listens' for named "spreadsheet cell" assignments to its namespace, and it "listens" for a repr access to the "spreadsheet" as a whole, presenting its status in terms of cell names and the formula value of the last cell entered. Not conventional, but I wanted to stay as close to the OP's proposed example interactive log (if that was what it was, which apparently it wasn't ;-) This does also demonstrate that if you want to "listen" for apparent assignments to bare names, AFAIK there is no way without byte code hackery or using a trace hook, or just doing your own eval-print loop, which is why I suggested the cmd module as a start. of course, you could mess with displayhook to get what the OP originally appeared to be asking for. E.g., this toy produces an interactive log much like the OP specified: >>> class DH(object): ... def __init__(self): ... import math ... self.env = vars(math) ... self.env.update(vars(__builtins__)) ... def evalstrex(self, s): ... for name in compile(s,'','eval').co_names: ... if type(self.env[name]) == str: ... self.env[name] = self.evalstrex(self.env[name]) ... return eval(s, self.env) ... def __call__(self, o): ... if type(o)==str: ... self.env.update(globals()) ... o = self.evalstrex(o) ... sys.__displayhook__(o) ... >>> import sys >>> sys.displayhook = DH() Other than the quotes around the formula, >>> a = '[sin(x), cos(x)]' >>> x=0.0 >>> a [0.0, 1.0] >>> x=1.0 >>> a [0.8414709848078965, 0.54030230586813977] looks a lot like """ I'm looking for array of functions. Something like a=[ sin(x) , cos(x) ] >>> x=0.0 >>> a [0, 1] >>> x=1.0 >>> a ... of course it can be made by >>> def cratearray(x): ... ~~~~ ... return a a=createarray(1.0) but this isn't what i am asking for. something automized. """ Of course, this is not what the OP _really_ wanted ;-) But it's kind of fun. Anything you type in quotes is evaluated using available global bindings plus the ones in the math module and __builtins__, and it's recursive, so if a name in the quoted formula refers to another string (which must be a valid expression), that is evaluated, and so on. This is "pull" based on interactive display trigger ;-) >>> x='pi/6' >>> a [0.49999999999999994, 0.86602540378443871] >>> x='pi/6' >>> a [0.49999999999999994, 0.86602540378443871] >>> x = 'pi/y' >>> y=6 >>> a [0.49999999999999994, 0.86602540378443871] >>> y=3 >>> a [0.8660254037844386, 0.50000000000000011] The display hook passes through non-strings, so you can box a string formula to see it: >>> [a] ['[sin(x), cos(x)]'] >>> [x] ['pi/y'] >>> [y] [3] You could specify your spread sheet: >>> a1,a2,a3=100,200,'sum([a1,a2])' >>> a1,a2,a3 (100, 200, 'sum([a1,a2])') >>> a1 100 >>> a2 200 >>> a3 300 ;-) > >(2) Pull model: lazy evaluation. Have some flag on whether an >independent quantity has been changed. When evaluating a dependent >quantity, survey its independent quantities recursively, and update the >cached copies whereever necessary. > >Of course, combination of the two approaches is possible. > >For Python, metaclasses and/or decorators and/or properties may help. > >But functional languages are a more natural territory. > Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
