W4_A1_Ex-10_updating length of the parameters

Course Q&A Deep Learning Specialization Neural Networks and Deep Learning
1

In this exercise, L = len (parameters)

parameters contains 4 elements: W1, W2, b1 and b2

Why is len(parameters) = 2?

2

Why do you believe that len(parameters) is 2?

3

The given code in the exercise is the following. This mentions that L = 2:

def update_parameters(params, grads, learning_rate):
“”"
Update parameters using gradient descent

Arguments:
params -- python dictionary containing your parameters 
grads -- python dictionary containing your gradients, output of L_model_backward

Returns:
parameters -- python dictionary containing your updated parameters 
              parameters["W" + str(l)] = ... 
              parameters["b" + str(l)] = ...
"""
parameters = copy.deepcopy(params)
L = len(parameters) // 2 # number of layers in the neural network
4

Please post a screen capture image.

5

image
image1700×698 85.6 KB

6

That doesn’t say that the length is 2.
It says to take the length and apply floor division by 2.
The comment says why.

7

Got it. Coming from c++, I interpreted the ‘//’ as the comment symbol.