[Numpy-discussion] lists of zeros and ones

[Keith Goodman]

On Fri, Mar 19, 2010 at 7:53 AM, gerardob <gberbeglia at gmail.com> wrote:
>
> Hello, i would like to produce lists of lists 1's and 0's.
>
> For example, to produce the list composed of:
>
> L = [[1,0,0,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]]
>
> I just need to do the following:
>
> n=4
> numpy.eye(n,dtype=int).tolist()
>
> I would like to know a simple way to generate a list containing all the
> lists having two 1's at each element.
>
> Example, n = 4
> L2 = [[1,1,0,0],[1,0,1,0],[1,0,0,1],[0,1,1,0],[0,1,0,1],[0,0,1,1]]
>
> Any ideas?
> Thanks.

Here's the brute force way:

>> for i in range(4):
   ....:     for j in range(i+1, 4):
   ....:         x = np.zeros(4)
   ....:         x[i] = 1
   ....:         x[j] = 1
   ....:         print x
   ....:
   ....:
[ 1.  1.  0.  0.]
[ 1.  0.  1.  0.]
[ 1.  0.  0.  1.]
[ 0.  1.  1.  0.]
[ 0.  1.  0.  1.]
[ 0.  0.  1.  1.]