CODEWITHSUNDEEP
pythonclass
Lukasz
Lukasz

Reputation: 2606

Python constructing a class that uses a function from within the same class

I'm trying to get a construct a class that calls a function from within the same class but I'm having trouble doing so.

I've had a look at:

Python function pointers within the same Class

But I've had no luck with the approach presented. I've created this simple example:

#### Libraries ####
# Third Party Libraries  
import numpy as np

#### Defines the activation functions ####
class sigmoid_class(object):
    def __init__(self, z):
        self.z = z

    def activation_fn(self):
        """The sigmoid function"""
        return 1.0/(1.0+np.exp(-self.z))

    def prime(self):
        """The derivative of the sigmoid function"""
        return activation_fn(self.z)*(1-activation_fn(self.z))

a = sigmoid_class(0)
print(a.prime())

when I test with print(a.activation_fn(0)) I get the desired output, but when I try `print(a.prime())

I get `NameError: name 'activation_fn' is not defined

I'm not sure how to fix this so that it functions properly

Upvotes: 0

Views: 108

Answers (4)

joel goldstick
joel goldstick

Reputation: 4483

So combining both points:

def prime(self):
    """The derivative of the sigmoid function"""
    return self.activation_fn()*(1-self.activation_fn())

activation_fn finds self.z for itself

Upvotes: 3

Martin Bonner supports Monica
Martin Bonner supports Monica

Reputation: 28987

It should actually be:

def prime(self):
    """The derivative of the sigmoid function"""
    return self.activation_fn()*(1-self.activation_fn())

Note that activation_fn does not need to be passed the z value as well - it looks that up from self.

Upvotes: 4

jhwang
jhwang

Reputation: 43

The comments are correct, you need reference self. because activation_fn is not defined in the scope of the method itself, and your method also doesn't take in any arguments.

Upvotes: 1

djhaskin987
djhaskin987

Reputation: 10057

def prime(self):
    """The derivative of the sigmoid function"""
    return self.activation_fn(self.z)*(1-self.activation_fn(self.z))

Or so. note the self.activation_fn instead of just activation_fn.

Upvotes: 2

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