神经网络训练功能的“错误：列表分配索引超出范围”

Question

我正在研究反向传播算法，并且在训练具有固定时期数的网络的功能上，我不断遇到以下索引错误：

File "backprop-seed.py", line 149, in train_network
    expected[row[-1]] = 1
IndexError: list assignment index out of range

功能如下：

def train_network(network, train, l_rate, n_epoch, n_outputs):
    for epoch in range(n_epoch):
        for row in train:
            outputs = forward_prop(network, row)
            expected = [0 for i in range(n_outputs)]
            expected[row[-1]] = 1
            backprop_err(network, expected)
            update_weights(network, row, l_rate)

我应该如何纠正此错误？