Robert Berman wrote:
> 
>  In [69]: l1=[(0,0)] * 4
> 
>  In [70]: l1
>  Out[70]: [(0, 0), (0, 0), (0, 0), (0, 0)]
> 
>  In [71]: l1[2][0]
>  Out[71]: 0
> 
>  In [72]: l1[2][0] = 3
>  ---------------------------------------------------------------------------
>  TypeError                                 Traceback (most recent call 
>  last)
> 
>  /home/bermanrl/<ipython console> in <module>()
> 
>  TypeError: 'tuple' object does not support item assignment
> 
>  First question, is the error referring to the assignment (3) or the 
>  index [2][0]. I think it is the index but if that is the case why does 
>  l1[2][0] produce the value assigned to that location and not the same 
>  error message.
> 
>  Second question, I do know that l1[2] = 3,1 will work. Does this mean 
>  I must know the value of both items in l1[2] before I change either 
>  value. I guess the correct question is how do I change or set the 
>  value of l1[0][1] when I specifically mean the second item of an 
>  element of a 2D array?
> 
>  I have read numerous explanations of this problem thanks to Google; 
>  but no real explanation of setting of one element of the pair without 
>  setting the second element of the pair as well.
> 
>  For whatever glimmers of clarity anyone can offer. I thank you.

Tuples are immutable. Replace them with lists and voila. l1=[[0,0]] * 4

But also realize that you are creating a list with 4 copies of one 
object [0,0]. Assigning to one changes all!


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