# -*- coding: utf-8 -*-

a=input('please input a: ')
b=input('please input b: ')
c=input('please input c: ')
a=float(a)
b=float(b)
c=float(c)
import math
def quadratic(a,b,c):
     if(b**2-4*a*c<0):
        print('wrong')
     else:
        aa=math.sqrt(b**2-4*a*c)
        
        x1=float((-b+aa)/(2*a))
        x2=float((-b-aa)/(2*a))
        return x1,x2
        pass


## 测试:

print('')
print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))
print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))

if quadratic(2, 3, 1) != (-0.5, -1.0):
    print('测试失败')
elif quadratic(1, 3, -4) != (1.0, -4.0):
    print('测试失败')
else:
    print('测试成功')

输出结果：

please input a: 2

please input b: 3

please input c: 1

quadratic(2, 3, 1) = (-0.5, -1.0)
quadratic(1, 3, -4) = (1.0, -4.0)
测试成功

注：本函数中测试结果与输入的a，b，c无关