ICM algorithm

[R Gibert]

I got this from the FAQ concerning the ICM algorithm:
[ QUOTE ]

P^m_i = prob. of mth place for ith player
P^m_i = sum_{k!=i} P^1_k*P^m-1_i(S_~k)
where S_~k is the stacks after removing the k'th stack.

The recursion is closed with:
P^1_i = S_i/sum_k S_k


[/ QUOTE ]
I don't understand this notation. I would like to rewrite this in Python. If some one could explain what the above syntax means, it would be helpful.