嘗試從類的函數中打印變量時在 python 中出錯

Question

 class Network(object):

        def __init__(self, sizes):

        def feedforward(self, a):
            for b, w in zip(self.biases, self.weights):
                a = sigmoid(np.dot(w, a)+b)
            return a

        def SGD(self, training_data, epochs, mini_batch_size, eta,
                test_data=None):

        def evaluate(self, test_data):
            test_results = [(np.argmax(self.feedforward(x)), y)
                            for (x, y) in test_data]
            return sum(int(x == y) for (x, y) in test_results)

    def sigmoid(z):
        return 1.0/(1.0+np.exp(-z))

我正在制作一個神經網絡（我當然省略了很多代碼，因為有很多代碼）並且在函數“前饋”中我有變量“a”，它返回激活函數。 培訓結束后，我想打印出該變量。 訓練是這樣開始的：

net=Network([784,30,10])
net.SGD(training_data, 5, 30, 3.0, test_data=test_data)

和我試圖打印出的代碼：

print(net.feedforward(a))

但我收到以下錯誤：

`Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2019.3.3\plugins\python-ce\helpers\pydev\_pydev_bundle\pydev_umd.py", line 197, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2019.3.3\plugins\python-ce\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "C:/Users/MyName/DeepLearningPython35/network.py", line 158, in <module>
    print(net.feedforward(a))
NameError: name 'a' is not defined`

Answer 1

a變量僅feedforward函數的局部范圍內可用。 行print(net.feedforward(a))嘗試使用預期在全局范圍內定義的變量再次調用該函數。 一種可能性是使其成為實例變量：

def feedforward(self, a):
    for b, w in zip(self.biases, self.weights):
        self.a = sigmoid(np.dot(w, a)+b)
    return self.a

因此，您可以稍后打印出分配給它的最后一個值。

print(net.a)