Polynomial class - list assignment index out of range

Question

Save people, I’m learning classes in python and created one for application with polynomials, but I’m not able to add two distinct polynomials, always appears the following error:

File "/home/Documents/python/Poo/polinomio.py", line 30, in P3 = P1 + P2 File "/home/Leticia/Documents/python/Poo/polinomio.py", line 19, in add sum.terms[i] = self.terms[i] + other[i] Indexerror: list assignment index out of range

In these attempts to solve, I even added an attribute to pass the dimension of the vector, but I remain in it, where I am missing?

class Polinomio:

    def __init__ (self, termos = None, n = 0):
        self.termos = termos or []
        self.n = [0] * n

    def __len__ (self):
        return len(self.termos)

    def __setitem__ (self, i, x):
        self.termos[i] = x

    def __getitem__(self, i):
        return self.termos[i] 

    def __add__ (self, other):
        soma = Polinomio(n = self.termos.__len__())
        for i in range(self.termos.__len__()):
            soma.termos[i] = self.termos[i] + other[i]
        return soma

    def print (self):
        print(self.termos)


p1 = Polinomio([1, 2, 3])
p2 = Polinomio([1, 2, 3])
p2.print()
p3 = Polinomio()
p3 = p1 + p2

Answer 1

[TL;DR]

Try it like this:

class Polinomio:

    def __init__ (self, termos = None, n = 0):
        self.termos = termos or []
        self.n = [0] * n

    def __len__ (self):
        return len(self.termos)

    def __setitem__ (self, i, x):
        self.termos[i] = x

    def __getitem__(self, i):
        return self.termos[i] 

    def __add__ (self, other):            
        return [x + y for x, y in zip(self.termos, other.termos)]

    def print (self):
        print(self.termos)

Testing:

p1 = Polinomio([1, 2, 3])
p2 = Polinomio([4, 5, 6])
print ('Termos de p1: ', p1.termos)
print ('Termos de p2: ', p2.termos)
print ('Soma de p1+p2: ', p1+p2)

Termos de p1:  [1, 2, 3]
Termos de p2:  [4, 5, 6]
Soma de p1+p2:  [5, 7, 9]

See working on repl.it.