[Python-3000] Best Practices essays

[Edward C. Jones]

Adam DePrince wrote:

> Now, as for your example m * [ n * [0]], I would exclude it from a best
> practices document.  If  your goal is to create a two dimensional array
> of numbers, it doesn't work.  The first part, n* [0] is right, you are
> creating a list of n zeros, and when you say l[x]=y you are replacing
> that element.  
> 
> The second part, m *, is wrong.  You are creating a list of m references
> to the same list of n zeros.  

I know its wrong. It was a mistake I made several times when I was 
earning Python. The m * [ n * [0]] problem is a dark corner of Python 
that exists because Python variables are really pointers. Unfortunately, 
this dark corner is visible to newbies. Which is why it needs to be 
mentioned.