NgFor with index as value in attribute

I have a simple ngFor loop which also keeps track of the current index. I want to store that index value in an attribute so I can print it. But I can't figure out how this works.

I basically have this:

<ul *ngFor="#item of items; #i = index" data-index="#i">

    <li>{{item}}</li>

</ul>

I want to store the value of #i in the attribute data-index. I tried several methods but none of them worked.

How can I store the index value in the data-index attribute?