# Numpy issues browsing

• posted
0

I currently am trying to get my head around some basic artificial “intelligence“, so I copied this code from the net:

``````import numpy as np

def sigmoid(x):
return 1.0/(1+ np.exp(-x))

def sigmoid_derivative(x):
return x * (1.0 - x)

class NeuralNetwork:
def __init__(self, x, y):
self.input      = x
self.weights1   = np.random.rand(self.input.shape,4)
self.weights2   = np.random.rand(4,1)
self.y          = y
self.output     = np.zeros(self.y.shape)

def feedforward(self):
self.layer1 = sigmoid(np.dot(self.input, self.weights1))
self.output = sigmoid(np.dot(self.layer1, self.weights2))

def backprop(self):
# application of the chain rule to find derivative of the loss function with respect to weights2 and weights1
d_weights2 = np.dot(self.layer1.T, (2*(self.y - self.output) * sigmoid_derivative(self.output)))
d_weights1 = np.dot(self.input.T,  (np.dot(2*(self.y - self.output) * sigmoid_derivative(self.output), self.weights2.T) * sigmoid_derivative(self.layer1)))

# update the weights with the derivative (slope) of the loss function
self.weights1 += d_weights1
self.weights2 += d_weights2

if __name__ == "__main__":
X = np.array([[0,0,1],
[0,1,1],
[1,0,1],
[1,1,1]])
y = np.array([,,,])
nn = NeuralNetwork(X,y)

for i in range(1500):
nn.feedforward()
nn.backprop()

print(nn.output)
``````

When importing numpy I got some error, but I fixed it by installing numpy via stash. But if sou try to execute this code in pythonista, you will get heaps of errors. For example, numpy.array() apparently doesn’t exist. Does anyone know why this is the case?

posted
0

Please don't try to install numpy via StaSh, it's simply not possible, and it may break the version that is included with Pythonista. I just tried your script in a vanilla Pythonista, and it seemed to work fine.

• posted
0

@omz ok, no problem. I just reinstalled Pythonista on my iPad. Obviously it functions now, thanks a lot. I’m sure you hear this frequently, but Pythonista is a great app. I’m just 16yrs old, so it helped a lot at learning coding in general.

• posted
0

@Drizzel said:

@omz ok, no problem. I just reinstalled Pythonista on my iPad. Obviously it functions now, thanks a lot. I’m sure you hear this frequently, but Pythonista is a great app. I’m just 16yrs old, so it helped a lot at learning coding in general.

Hopefully I didn’t agree that I’m over 18 when signing up this forum :D

• posted
1

@Drizzel I've a lot of years too much, thus feel free to take some of mine 😂

• posted
1

One thing that can happen sometimes it's if you hit X right after running a script. Since numpy or matplotlib are very large, importing them takes some time. If you cancel before the import is complete, you get a partial import, which breaks later imports.

Internal error.

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