Python second class initialization

Question

I have my first task on python class:

Create a module vectors.py
It will be a class definition MyVector
constructor will accept one parameter, which will be one-dimensional array.
get_vector() method returns one-dimensional array containing the elements of the vector.
using a special method __ mul__(self, other) implement the dot product of two objects of type MyVector. The output is a scalar (a single number).

Now it's seems like this:

class MyVector:
    def __init__(self,vector=[]):
        self.vector=vector

    def get_vector(self):
        return (self.vector)        

    def __mul__(self,other):
        dot=sum(p*q for p,q in zip(self.vector, WHAT IS HERE?))
        return(dot)

I have first vector, but how can I initialize second?

Ashwini Chaudhary · Accepted Answer · 2012-09-30 13:20:57Z

3

If you assume that the other parameter for the special __mul__ method is an instance of MyVector, then that instance will also have an attribute named vector which you can access:

def __mul__(self,other):
    dot=sum(p*q for p,q in zip(self.vector, other.vector))
    return (dot)

and don't use [] as default value in function arguments, use something like this :

 def __init__(self,vector=None):
    self.vector=vector if vector else []

edited Sep 30, 2012 at 13:20

Ashwini Chaudhary

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answered Sep 30, 2012 at 13:17

buc

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1 Comment

Jon Clements Over a year ago

Using None as a "sentinel", then self.vector = vector if vector is not None else [] is perhaps more correct. Also, more for the OP, it's probably best to use other.get_vector() to preserve duck typing and preserve an interface to a class

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