input = open('in.txt', 'r')
output = open('out.txt', 'w')
linesarray = input.readlines()
input.close()
seen = []
for i in range(len(linesarray)):
if seen.count(linesarray[i]) == 0:
seen.append(linesarray[i])
output.write(linesarray[i])
output.close() Между прочим в гугле нашла