【我确保了输入的a,b,c一定是整数或浮点数】

import math

def quadratic(a,b,c):

    if not isinstance(a,(int,float)):

        raise TypeError('bad operand type')

    elif not isinstance(b,(int,float)):

        raise TypeError('bad operand type')

    elif not isinstance(a,(int,float)):

        raise TypeError('bad operand type')

    elif (b*b-4*a*c)<0:

        return('无解')

    elif (b*b-4*a*c)==0:

        x0=(-b)/(2*a)

        return (x0)        

    else:

        x1=(-b-math.sqrt(b*b-4*a*c))

        x2=(-b+math.sqrt(b*b-4*a*c))

        return(x1,x2)

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

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

print('quadratic(1.78,4.23,-4.8963)=',quadratic(1.78,4.23,-4.8963))

print('quadratic(1,6,9)=',quadratic(1,6,9))

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')

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')