求加权平均值，没看懂错误在哪里，望求解

from operator import mul

def main(values, weights):
    f=0
    z=0
    for a,b in values,weights:
        s=mul(a,b)
        z=z+a
        f=f+s
    return f/z
    
if __name__ == "__main__":
    values, weights = eval(input())
    res_result = main(values, weights)
    print(res_result)

 
from operator import mul
 
def main(values, weights):
    f=0
    z=0
    for n in range(len(values)):
       f = f + (values[n] * weights[n])
       z = z + weights[n]
    return f/z
    
if __name__ == "__main__":
    values, weights = eval(input())
    res_result = main(values, weights)
    print(res_result)