请问大佬为什么重写del后调用时还会删除变量？

class Test:
        def __del__(self):
                print(1)

                
>>> a = Test()
>>> del a
1
>>> a
Traceback (most recent call last):
  File "<pyshell#14>", line 1, in <module>
    a
NameError: name 'a' is not defined

class FileObject:
    '''给文件对象进行包装从而确认在删除时文件流关闭'''

    def __init__(self, filename='sample.txt'):
        #读写模式打开一个文件
        self.new_file = open(filename, 'r+')

    def __del__(self):
        self.new_file.close()
        del self.new_file