Text12. Дана строка S и текстовый файл. Заменить в файле все пустые строки на строку S.

Решение на Python 3:

# -*- coding: utf-8 -*-
import random
import string
import os
import sys
import codecs

def RndString():
    ru_letters = u"абвгдеёзийклмнопрстуфхъыьэАБВГДЕЁЗИЙКЛМНОПРСТУФХЪЫЬЭ"
    en_letters = u"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    tj_letters = u"ғӣқӯҳҷҒӢҚӮҲҶ"

    N = random.randrange(1,10)
    s_ru = random.sample(ru_letters, N)
    s_en = random.sample(en_letters, N)
    s_tj = random.sample(tj_letters, N)
    s_digit = random.sample(string.digits, N)
    s = s_ru + s_en + s_tj + s_digit + [' ',' ']
    random.shuffle(s)
    rnd_str = "".join(s)
    return rnd_str


#file for reading and adding empty row
file1 = "text12_1.txt"

#file for temporary data
N = random.randrange(5,8)
S = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(N))
temp_file = "temp_" + S + ".txt"
temp_file = "text12_2.txt"
print("Temp file:",temp_file)
print("Write to:",temp_file)

rnd_str = RndString()
print("String:",rnd_str)

with codecs.open(file1, 'r', 'utf-8') as infile:
    with codecs.open(temp_file, 'w', 'utf-8') as outfile:
        for line in infile:
            if line.strip("\r\n") != "":
                outfile.write(line)
            else:
                outfile.write(rnd_str+"\r\n")
sys.exit()

print("Rename {0} to {1}".format(temp_file,file1))
try:
    os.rename(temp_file, file1)
except WindowsError:
    os.remove(file1)
    os.rename(temp_file, file1)
except OSError as e:
    print("Error:", e)