Numpy 抛出 TypeError: cannot unpack non-iterable NoneType object

Question

I have code directly copy pasted from https://blog.varunajayasiri.com/numpy_lstm.html . The code fails on line 195, or:

for t in reversed(range(len(inputs))):
    y_val = y_s[t]
    # Backward pass
    dh_next, dC_next = \
        backward(target = targets[t], dh_next = dh_next,
                 dC_next = dC_next, C_prev = C_s[t-1],
                 z = z_s[t], f = f_s[t], i = i_s[t], C_bar = C_bar_s[t],
                 C = C_s[t], o = o_s[t], h = h_s[t], v = v_s[t],
                 y = y_val)

I manually set y_val so I could check the value, and when checking right before the crash, it clearly prints a numpy array, but when it gets to backward , it crashed. Changing y to anything else, say as an example:

backward(target = targets[t], dh_next = dh_next,
                     dC_next = dC_next, C_prev = C_s[t-1],
                     z = z_s[t], f = f_s[t], i = i_s[t], C_bar = C_bar_s[t],
                     C = C_s[t], o = o_s[t], h = h_s[t], v = v_s[t],
                     y = 4)

And the code runs perfectly fine (only crashing due to an assertion error inside the function due to shape mismatch). It also runs fine if I set it to some random numpy array:

backward(target = targets[t], dh_next = dh_next,
                     dC_next = dC_next, C_prev = C_s[t-1],
                     z = z_s[t], f = f_s[t], i = i_s[t], C_bar = C_bar_s[t],
                     C = C_s[t], o = o_s[t], h = h_s[t], v = v_s[t],
                     y = np.array[1,2,3,4,5,6,7,8,9])

Again only crashes due to the assertion error.

Does anyone know what's going on here? I am very confused.

Here's the full error:

data has 43 characters, 28 unique
Traceback (most recent call last):
  File "C:\Users\a\Desktop\stuff\b\lstm\example_lstm.py", line 287, in <module>
    forward_backward(inputs, targets, g_h_prev, g_C_prev)
  File "C:\Users\a\Desktop\stuff\b\lstm\example_lstm.py", line 195, in forward_backward
    y = y_val)
TypeError: cannot unpack non-iterable NoneType object

Answer 1

It was a problem with the traceback. Turns out it was actually getting inside the function, and then throwing an error on a for loop inside the function, but for some reason wasn't giving any indication that is is where it was crashing. Very strange, maybe it's a bug to do with non-iterable TypeError's? Not sure, none-the-less that's what was going on.