How do I make a list where each item occurs a different number of times?

Question

I have two list one is list1=[], second is list2=["a","b","c"], I need to let list1=["a","a","a","b","b","c"], what should I do? In addition, the list2 can be anything , if it has 20 elements, the "a" should *20.

Answer 1

I know very little Python, so this might not be the best way of doing it, but it seems to work.

list1 = []
list2 = ["a", "b", "c"]
for x in range(len(list2)):
    list1 += [list2[x]] * (len(list2) - x)
print(list1)

Answer 2

Here's the same idea but with a one liner list comprehension:

list2 = ["a", "b", "c"]
list1 = [y for idx, x in enumerate(list2) for y in x * (len(list2) - idx)]
print(list1)