I'm trying to solve the following challenge
https://www.hackerrank.com/challenges/s10-weighted-mean/problem?h_r=next-challenge&h_v=zen


On my jupiter notebook the following function solves it:
 
```
def weightedMean(X, W):  
     # Write your code here  
     dotprd=sum([x*w for (x,w) in zip(X,W)])  
     return dotprd/sum(W)
```


However, on the site of the challenge, my function returns nothing... 


> ~ no response on stdout ~

why is that?