w_file = open("md.txt", 'a', encoding="utf-8")

for i in range(1, 11):
    in_file = open(f"4.2/{i}.py", "r", encoding="utf-8")
    w_file.write("\n/py\n")
    for s in in_file:
        w_file.write(s)
    in_file.close()