def multiply(a,b):
    """
    Args:
        + a: a list, like [a1,a2]
        + b: a list, like [b1,b2]
    Returns:
        a1b1+a2b2
    """
    #a,b两个列表的数据一一对应相乘之后求和
    sum_ab=0.0
    for i in range(len(a)):
        temp=a[i]*b[i]
        sum_ab+=temp
    return sum_ab