python recursive iteration derivative polynomial function

Question

I am trying to write a class that initialises certain parameters that are to be use over again in different methods. However when I write a simple recursive algorithm based on initialised values I always get an error message and I really don't know how to solve it myself.

Here is what the algorithm should look like:

def normal_recursion(poly):

    if len(poly) == 1:
        return poly[0]

    else:
        return poly[0] + normal_recursion(poly[1:])

>>> print(normal_recursion([1,2,3]))
>>> 6

which is exactly what should come out.

Now my class looks like:

class Ps2(object):

    def __init__(self, poly):
        self.poly = poly


    def testFunction(self):

        '''Computes the sum of the elements of an indexable object.'''

        if len(self.poly) == 1:
            return self.poly[0]

        else:
            return self.poly[0] + self.testFunction(self.poly[1:])

if:

test = Ps2([1,2,3])

and:

test.testFunction()

then:

TypeError: testFunction() takes 1 positional argument but 2 were given

I have tried all kinds of variations of 'def testFunction(self):' like 'def testFunction(self, self.poly)' but non of them were successful.

However, there is a related question here on Stackoverflow: Python Recursion within Class and I should mention that this algorithm works.

The difference to my problem is that I want to used the values from def init(): as the input for my method.

Anyway, your help is really being appreciated.

Joran Beasley · Accepted Answer · 2014-07-28 16:29:40Z

2

def testFunction(self,poly = None):

    '''Computes the sum of the elements of an indexable object.'''
    poly = self.poly if poly is None else poly
    if len(poly) == 1:
        return poly[0]

    else:
        return poly[0] + self.testFunction(poly[1:]) #since you send it an argument here you must have a argument in the function declaration

answered Jul 28, 2014 at 16:29

Joran Beasley

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1 Comment

Vincent Over a year ago

Just changed the comment. Great help really. I could not have come up with that approach.

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