```
board = [["bRook", "bKnight", "bBishop", "bQueen", "bKing", "bBishop", "bKnight", "bRook"],
         ["bPawn", "bPawn",   "bPawn",   "bPawn",  "bPawn", "bPawn",   "bPawn",   "bPawn"],
         ["",      "",        "",        "",       "",      "",        "",        ""],
         ["",      "",        "",        "",       "",      "",        "",        ""],
         ["",      "",        "",        "",       "",      "",        "",        ""],
         ["",      "",        "",        "",       "",      "",        "",        ""],
         ["wPawn", "wPawn",   "wPawn",   "wPawn",  "wPawn", "wPawn",   "wPawn",   "wPawn"],
         ["wRook", "wKnight", "wBishop", "wQueen", "wKing", "wBishop", "wKnight", "wRook"]]

def evaluation():
#Material Score
materialScoreWhite = 0
materialScoreBlack = 0
#Main Material
pieceScores = {"Pawn": 100,
               "Knight": 320,
               "Bishop": 330,
               "Rook": 500,
               "Queen": 900,
               "King": 20000}

    for each in board:
        for f in each:
            if f[0] == "w":
                materialScoreWhite += "w" + pieceScores[each[0:]]
            elif f[0] == "b":
                materialScoreBlack += "b" + pieceScores[each[0:]]

```

I am trying to make a simple chess engine in Python. The list `board` shows how the board is in the position the program is trying to evaluate. Part of my evaluation involves going through each piece on the board and adding a certain value to the score that colour has. 

For example, the first piece in the list at the moment (the starting position) is a black rook so I want the program to add `500` to `materialScoreBlack`. However, I keep getting this error: 

```
    materialScoreBlack += "b" + pieceScores[each[0:]]
TypeError: unhashable type: 'list'

```

How can I fix this?