[Tutor] Encoding and Decoding

[Carlos]

Kent,

Will give this a try.

Thanks for your help,
Carlos


Kent Johnson wrote:
> OK, off the top of my head (not tested) here are some things to get 
> you started.
>
> You could write a function that would retrieve a coordinate value 
> given an index number, for example:
> def getCoord(data, ix):
>   base = ix*4
>   value = data[ix]*10 + data[ix+1] + data[ix+2]/10.0
>   if data[ix+3] < 5:
>     value = -value
>   return value
>
> Now if data is your big list, you can write getCoord(data, 5) to get 
> the value stored at data[20] to data[23]. Similarly you could write a 
> setter and maybe a getXY() function that returns a pair (x, y). So 
> that is a place to start.
>
> If you want to avoid passing the list around it might make sense to 
> make a class to hold it. Then you would have something like
> class Data(object):
>   def __init__(self, lst):
>     self.data = lst
>
>   def getCoord(self, ix):
>     base = ix*4
>     value = self.data[ix]*10 + self.data[ix+1] + self.data[ix+2]/10.0
>     if self.data[ix+3] < 5:
>       value = -value
>     return value
>
> Now you can create a Data object from a list of values and ask it for 
> values:
> d = Data(<some list>)
> d.getCoord(5)
>
> I'm not sure this is much improvement over passing around the list, 
> actually; you still have to pass around the Data object...it might 
> just be a matter of taste.
>
> HTH,
> Kent