write_to_file

f = open('data.txt', 'r')

L = []

for line in f.readlines():
    L.append(line)

line_number = len(L)+1
f.close()

name = 'Timofey '
surname = 'Kukushkin '
pay = '(1)'

f1 = open('data.txt', 'a')
f1.writelines(str(line_number) + '.' + name + surname + pay+'\n')
f1.close()