def alter(file,old_str,new_str):
  file_data = ""
  with open(file, "r", encoding="utf-8") as f:
    for line in f:
      if old_str in line:
        line = line.replace(line,new_str)
      file_data += line
  with open(file,"w",encoding="utf-8") as f:
    f.write(file_data)
    f.close()
code_pro = 'mycode'
code = f"secret_code = '{code_pro}'"
alter("/Users/xc/Desktop/conf.toml", "secret_code", code)