Creating duplicate integers in list

Question

Create a function that duplicates every integer in a list
I have to write a function that accepts a list of integers as a parameter and replaces every element with two copies of itself. For example, if a list named nums stores [1, 2, 3], the call of stutter(nums) should change it to store [1, 1, 2, 2, 3, 3].
This is what I tried, but rather than creating and printing a new list (b), how do I change the values in the original lists that is passes in as a parameter? I'm just trying to modify the original list (a) but the error it's giving me is unsupported 'int' type error because it's reading my integer list as a string.
def stutter(a):
b = []
for i in a:
b.extend([i, i])
return b
stutter([1, 2, 3])

Answer 1

def stutter(l):
return [y for x in zip(l, l) for y in x]
stutter([1, 2, 3])

Answer 2

This does what your looking for:
https://code.sololearn.com/ce7Ny5rxSJKx