how to define the size of a list?

[Marco Herrn]

Alex Martelli schrieb im Artikel <_4Cy9.6277$XO.267683 at news2.tin.it>:
> Marco Herrn wrote:
> 
>> Sorry if that is a stupid question, but I didn't find the answer in the
>> docu. I want to define a matrix (a 2-dimensional list) with a specific
>> size. But I didn't find a way to set the size of the list at creation
>> time.
>> 
>> So how can I do this?
> 
> You can create a list of length N in many ways, such as:
>     x = N * [0]
>     x = [ 0 for i in range(N) ]
>     x = range(N)
> and so on, depending on what initial contents you want the
> length-N list to have.
> 
> There are no "two-dimensional" lists in Python proper (and
> you don't mention using the Numeric extension, which DOES
> have them), so I think you mean a list of lists.

Yes, that is what I want.

>  In this
> case, take care NOT to use the first form for the outer level,
> or that would give you a list containing N copies of the SAME
> inner list -- surely not what you want.  I.e., to make a list
> of N separate sublists, each sublist made up of N 0's, do:
>     x = [ [0]*N for i in range(N) ]

Thanks, that helps me.

Bye
Marco


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