Replacing one element of a mutable list with one element of another mutable list

Question

Can anyone spot why my code replaces all the elements in my blanks list instead of just the first one, as I am trying to ask it?

Here is my code:

https://code.sololearn.com/cxSAz3Eyc5qK/?ref=app

Answer 1

After a couple of minutes of research, I came up with this. Hope this is helpful.

https://code.sololearn.com/cy84q472AF63/?ref=app