问如何打印在Python中系数已知的n次多项式的字符串表示？

EN

class Poly():
    def __init__(self, coeff):
        self.coeff = coeff
        self.N = len(coeff)

    def evaluate(self, x):
        res = 0.0
        for i in range(self.N):
            res += self.coeff[i] * (x**(self.N-i-1))
        return res

    def printPoly(self):
        for i in range(self.N):
            if i == self.N-1:
                print("%f" % (abs(self.coeff[i])))
            else:
                if self.coeff[i] != 0.0:
                    print("%f * x**%d" % (abs(self.coeff[i]), self.N-i-1), end='')
                    if self.coeff[i+1] > 0:
                        print(" + ", end='')
                    else:
                        print(" - ", end='')

p = poly([1,-2,5]) # creating the polynomial object.
p.printPoly() # prints: 1.0 * x**2 - 2.0 * x**1 + 5
print(p.evaluate(0.0)) # prints: 5.0

import sympy 
from sympy import poly

x = sympy.Symbol('x') # Create a symbol x

coefficients = [1,-2,5] # Your coefficients a python list

p1 = sum(coef*x**i for i, coef in enumerate(reversed(coefficients))) # expression to generate a polynomial from coefficients.

print p1 # print(p1), depending on your python version