Hi, I would need some help to figure out why I get error in optimize() function:
I counted grads and costs like this:
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Why does it return “TypeError: ‘float’ object is not subscriptable”?
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learning_rate is a float. You can use it directly like x -= learning_rate * y
The learning rate is a Python float object, i.e. a floating point number. For example the statement learning_rate = .01 implies that learning_rate is of Python type float. You have apparently tried to access an element of learning_rate as if it were an iterable (e.g. a Python list object). That would like something like learning_rate[0] to access the first element. Since learning_rate is not an iterable, but rather a float, your code has thrown the TypeError exception. You need to think about whatever logic you applied to arrive at the conclusion that learning_rate is “list-like”. 
Thank you for your response and help! It was a stupid mistake from me, I got confused because of for-loop and tried to force index i somewhere. Problem is solved now.