Python Compute the value of a function as a polynomial

def qpoly(a,b,c,x):
    return a*x*x+b*x+c

def plot(a,b,c,x1,x2):
    alist = []
    while (x2-x1) >=0 :
       alist.append(qpoly(a,b,c,x1))
       x1 = x1+1
    return alist