from collections import Counter

coffees_per_day = [1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 6]
frequency = Counter(coffees_per_day)

for value in sorted(frequency):
    count = frequency[value]
    bar = "*" * count
    print(f"{value} cups: {count:>2}  {bar}")

# Output:
# 1 cups:  2  **
# 2 cups:  5  *****
# 3 cups:  7  *******
# 4 cups:  4  ****
# 5 cups:  1  *
# 6 cups:  1  *