class Polynomial:
    def __init__(self, coefficients):
        self.coeff = coefficients

    def __call__(self, x):
        """Evaluate the polynomial."""
        s=0
        for i in range(len(self.coeff)):
            s += self.coeff[i]*x**i
        return s

    def __add__(self, other):
        """Return self + other as Polynomial object."""
        # Two cases:
        #
        # self:  XXXXXXXX
        # other: XXXX
        #
        # or:
        #
        # self: XXXX
        #other: XXXXXXXX
        # Start with the longest list and add in the other
        if len(self.coeff) > len(other.coeff):
            result_coeff = self.coeff[:]  # copy!
            for i in range(len(other.coeff)):
                result_coeff[i] += other.coeff[i]
        else:
            result_coeff = other.coeff[:] # copy!
            for i in range(len(self.coeff)):
                result_coeff[i] += self.coeff[i]
        return Polynomial(result_coeff)

    def __sub__(self,other):
        """Return self - other as Polynomial object."""
        # Two cases:
        #
        # self:  XXXXXXXX
        # other: XXXX
        #
        # or:
        #
        # self: XXXX
        #other: XXXXXXXX
        if len(self.coeff) > len(other.coeff):
            result_coeff = self.coeff[:]  # copy!
            for i in range(len(other.coeff)):
                result_coeff[i] -= other.coeff[i]
        else:
            result_coeff = [0]*len(other.coeff)
            result_coeff[:len(self.coeff)] = self.coeff[:]
            for i in range(len(other.coeff)):
                result_coeff[i] -= other.coeff[i]
        return Polynomial(result_coeff)


p1 = Polynomial([1, -1])  #p1 = 1-x
p2 = Polynomial([0, 1, 0, 0, -6, -1]) #p2 = x - 6*x**4 -x**5
p3 = p1 + p2  #p3 = 1 - 6*x**4 -x**5
print(p3.coeff)
p4 = p1-p2  # -1 - 2*x + 6*x**4 + x**5 [-1,-2,0,0,6,1]
print(p4.coeff)

"""
Terminal> python polynomial_sub.py
[1, 0, 0, 0, -6, -1]
[1, -2, 0, 0, 6, 1]
"""