py: sort a list and delete dup

s='2199935567778'
list=[]
prev=0
for i in s:
    list.append(int(i))
list.sort()
print (list)
for digit in list:
    if digit!=prev:
        print(digit)
    prev=digit

Delete duplicates from file (Yandex task)

with open('input.txt', 'r') as f:
    n = int(f.readline())
    prev = 0
    for i in range(n):
        val = f.readline()
        if val != prev:
            print(val)
        prev = val