python实现一元二次表达式求值

import math
import cmath
flag="yes"
while True:
    flag= (input("是否计算新方程的根："))
    if (flag=="yes"):
        print('a*x*x+b*x+c=0')
        a= float (input('a='))
        b= float (input('b='))
        c= float (input('c='))
        p=b*b-4*a*c

        if p<0:
            pp=str("√"+str(-p))
            x1=str((-b)/(2*a))+"+"+str((1/2/a))+pp+"i"
            x2=str((-b)/(2*a))+"-"+str((1/2/a))+pp+"i"
            print("无实根，两个虚根："+str(x1),str(x2))

        if p>0:
            x1 = (-b+math.sqrt(p))/(2*a)
            x2 = (-b-math.sqrt(p))/(2*a)
            print("两个不相等的实根："+str(x1),str(x2))
        if p==0:
            x1 = (-b + math.sqrt(p)) / (2 * a)
            print("两个相等的实根："+str(x1))


    else:
        break;