import idx2numpy import numpy as np # 导入训练集和训练集对应的标签并将其初始化 X_train, T_train = idx2numpy.convert_from_file('emnist/emnist-letters-train-images-idx3-ubyte'), idx2numpy.convert_from_file('emnist/emnist-letters-train-labels-idx1-ubyte') X_train, T_train = X_train.copy(), T_train.copy() X_train = X_train.reshape((X_train.shape[0], -1)) T_train = T_train - 1 T_train = np.eye(26)[T_train] # 导入测试集和测试集对应的标签标签并将其初始化 X_test, T_test = idx2numpy.convert_from_file('emnist/emnist-letters-test-images-idx3-ubyte'), idx2numpy.convert_from_file('emnist/emnist-letters-test-labels-idx1-ubyte') X_test, T_test = X_test.copy(), T_test.copy() X_test = X_test.reshape((X_test.shape[0], -1)) T_test = T_test - 1 T_test = np.eye(26)[T_test]。补写成一个用人工神经网络识别手写字母图片的程序，包含n个隐藏层

好的，我可以为您提供一个简单的多层感知机(MLP)神经网络程序。该程序包含1个输入层、n个隐藏层和1个输出层。您可以根据需要自行调整隐藏层数量和每个隐藏层的神经元数量。

import idx2numpy
import numpy as np

class MLP:
    def __init__(self, input_size, hidden_sizes, output_size):
        self.input_size = input_size
        self.hidden_sizes = hidden_sizes
        self.output_size = output_size

        sizes = [input_size] + hidden_sizes + [output_size]
        self.weights = [np.random.randn(sizes[i], sizes[i+1]) for i in range(len(sizes)-1)]
        self.biases = [np.random.randn(size) for size in sizes[1:]]

    def forward(self, X):
        self.hidden_layers = []
        self.activations = [X]

        for i in range(len(self.weights)-1):
            z = np.dot(self.activations[-1], self.weights[i]) + self.biases[i]
            h = self.sigmoid(z)
            self.hidden_layers.append(h)
            self.activations.append(h)

        z = np.dot(self.activations[-1], self.weights[-1]) + self.biases[-1]
        y = self.softmax(z)
        self.activations.append(y)

        return y

    def backward(self, X, y, output):
        delta = output - y
        self.weights[-1] += self.hidden_layers[-1].T.dot(delta)
        self.biases[-1] += np.sum(delta, axis=0)

        for i in range(len(self.weights)-2, -1, -1):
            delta = delta.dot(self.weights[i+1].T) * self.sigmoid_derivative(self.hidden_layers[i])
            self.weights[i] += self.activations[i].T.dot(delta)
            self.biases[i] += np.sum(delta, axis=0)

    def train(self, X, y, epochs, learning_rate):
        for epoch in range(epochs):
            for i in range(len(X)):
                output = self.forward(X[i])
                self.backward(X[i], y[i], output)

    def predict(self, X):
        y_pred = []
        for i in range(len(X)):
            output = self.forward(X[i])
            y_pred.append(np.argmax(output))
        return y_pred

    def sigmoid(self, z):
        return 1 / (1 + np.exp(-z))

    def sigmoid_derivative(self, z):
        return z * (1 - z)

    def softmax(self, z):
        exp_z = np.exp(z)
        return exp_z / np.sum(exp_z, axis=1, keepdims=True)

# 加载训练集和训练集对应的标签
X_train, T_train = idx2numpy.convert_from_file('emnist/emnist-letters-train-images-idx3-ubyte'), idx2numpy.convert_from_file('emnist/emnist-letters-train-labels-idx1-ubyte')
X_train, T_train = X_train.copy(), T_train.copy()
X_train = X_train.reshape((X_train.shape[0], -1))
T_train = T_train - 1
T_train = np.eye(26)[T_train]

# 加载测试集和测试集对应的标签
X_test, T_test = idx2numpy.convert_from_file('emnist/emnist-letters-test-images-idx3-ubyte'), idx2numpy.convert_from_file('emnist/emnist-letters-test-labels-idx1-ubyte')
X_test, T_test = X_test.copy(), T_test.copy()
X_test = X_test.reshape((X_test.shape[0], -1))
T_test = T_test - 1
T_test = np.eye(26)[T_test]

# 初始化神经网络模型
mlp = MLP(input_size=X_train.shape[1], hidden_sizes=[50, 50], output_size=26)

# 训练神经网络模型
mlp.train(X_train, T_train, epochs=10, learning_rate=0.1)

# 在测试集上评估神经网络模型
y_pred = mlp.predict(X_test)
accuracy = np.mean(y_pred == np.argmax(T_test, axis=1))
print("Test accuracy: {:.2f}%".format(accuracy * 100))

在上面的代码中，`MLP`类表示多层感知机(MLP)神经网络模型，其中`__init__`方法初始化神经网络的权重和偏置，`forward`方法执行前向传播，`backward`方法执行反向传播，`train`方法训练神经网络模型，`predict`方法对新样本进行预测，以及一些其他辅助函数。在主程序中，我们加载训练集和测试集数据，初始化神经网络模型，训练神经网络模型，并在测试集上评估神经网络模型的性能。