Evaluating polynomial using python -

i'm trying create own polynomial class. want make function can evaluate polynomial x given.

so far have this, answers giving me aren't right , cant figure out why? polynomials inputted using list. example [2, 0, 1, -7, 13] 2x^4+x^2-7x+13

class polynomial:  def __init__(self, coefficients):     self.coeffs=coefficients  def evaluate(self, x):     sum = 0     in range(len(self.coeffs)-1,0,-1):         sum+=self.coeffs[i]*(x**i)     return sum 

the i value you're using isn't right both index , exponent. you're evaluating reversed-coefficeint polynomial, evaluation results polynomial([2,3,4]) right value polynomial([4,3,2]).

here's how i'd define evaluate:

def evaluate(self, x):     return sum(coef * x**exp exp, coef in enumerate(reversed(self.coeffs))) 

note if want polynomial objects callable (as in p1(4) in example in comment), should rename evaluate function __call__.