how to append to every second item in list python

a=[2,4,6]
for b in range (0,len(a)):
    a.insert(b*2,1)

Here is what the above code is Doing:
1. It’s creating a list called a.
2. It’s creating a for loop that iterates through the list a.
3. It’s inserting the value 1 at the beginning of the list a.
4. It’s inserting the value 1 at the end of the list a.
5. It’s inserting the value 1 at the third position in the list a.

The output of the code should be:
[1, 2, 1, 4, 1, 6, 1]