def clear_space():

    with open("test","r",encoding="utf-8") as fr:

        for line in fr:

            line = line.strip()

            if len(line) > 0:

                yield line

g = clear_space()

for line in g:

    with open("test.bak","a",encoding="utf-8") as fw:

        fw.write(line+"\n")     ```