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def floydWarshall(self) :
    
    n = len(self._W)
    D = copy.deepcopy(self._W)
    P = copy.deepcopy(self._W)

    for i in range(n) :
        for j in range(n) :
            if i == j or self._W[i][j] == math.inf :
                P[i][j] = None
            else :
                P[i][j] = i

    for k in range(n) :
        for i in range(n) :
            for j in range(n) :
                if D[i][k] + D[k][j] < D[i][j] :
                    D[i][j] = D[i][k] + D[k][j]
                    P[i][j] = P[k][j]
    return D, P

I am trying to implement the floyd warshall algorithm. I am attempting to return the matrix that contains the predecessors of the matrix represented by P and a matrix D that consists of the weights between the shortest paths between vertices. I believe the the problem may be with my predecessor matrix, because it will return none in one case,

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  • 3
    As far as I can tell there is no way that this function returns None. It always returns a tuple. Commented Apr 15, 2022 at 17:12
  • Ok I suppose I have not isolated my problem properly then. Commented Apr 15, 2022 at 17:14
  • "in one case" in which case? Commented Apr 15, 2022 at 17:17
  • Well I thought it might have had something to do with "P[i][j] = None" since im returning D, P Commented Apr 15, 2022 at 17:18
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