How to convert a dictionary to a list of keys, with repeat counts given by the values?

Question

I need your help to solve a problem.

I want to convert a dictionary d = {key1:value1, key2:value2} into list= [keys1, keys1, ... (value1 times), k

Answer 1

d1={4:1,3:2,12:2} 
ans =[]
for key,value in d1.items():
    ans.append((str(key),)*value)
print(ans)
flattened = []
list(flattened.extend(item) for item in ans)
print(flattened)

Output:

[('4',), ('3', '3'), ('12', '12')]
['4', '3', '3', '12', '12']