list1 = [13, 19, 13, 2, 16, 6, 5, 19, 20, 21, 20, 13, 19, 13, 16]
frequency_list = {}
for l in list1:
    if l in frequency_list:
        frequency_list[l] += 1
else:
    frequency_list[l] = 1
print(frequency_list)
Counting frequencies in two lists, Python