python append to 2d array

temp_list = [[], [], [], []]
temp_list[0].append("a1")
temp_list[1].append("a2")
temp_list[2].append("a3")
temp_list[3].append("a4")

Here is what the above code is Doing:
1. Create a list of 4 empty lists.
2. Append “a1” to the first list.
3. Append “a2” to the second list.
4. Append “a3” to the third list.
5. Append “a4” to the fourth list.