报告使用内部循环重写循环变量的情况:
    for i in range(5):
      for i in range(20, 25):
          print("Inner", i)
      print("Outer", i)
  
如果在 with 语句中声明的变量在语句体中重新声明,它也会向您发出警告:
    with open("file") as f:
      f.read()
      with open("file") as f: