list

How can I remove list inside list?

I have a list like this [1, 2, 3, [4, 5, 6]]
How can I remove [ character inside the list so I can get [1, 2, 3, 4, 5, 6]?
This is my code so far:
a = [1, 2, 3, [4, 5, 6]]
new_a = []
for item in a:
if len(item) > 1:
for sub_…