Python 关闭文件释放内存的疑惑

 我用with语句打开了一个4g的文件读取内容，然后程序末尾设置一个死循环，按理说with语句不是应该自动关闭文件释放资源吗？

但是系统内存一直没有释放。应该是被文件读取到的变量content一直占用吗？把content删除就会释放内存。或者去掉死循环，程序退出资源就自动释放了

既然这样的话关闭文件貌似没啥作用呢？具体释放了什么资源？

Python一直占用着将近5G的内存：

官方文档：

If you’re not using the with keyword, then you should call f.close() to close the file and immediately free up any system resources used by it. If you don’t explicitly close a file, Python’s garbage collector will eventually destroy the object and close the open file for you, but the file may stay open for a while. Another risk is that different Python implementations will do this clean-up at different times.

After a file object is closed, either by a with statement or by calling f.close(), attempts to use the file object will automatically fail.

 代码如下：

import sys
with open(r'H:\BaiduNetdiskDownload\4K.mp4','rb') as f:
    print(f.closed)
    content=f.read()
print(f.closed)
print(sys.getrefcount(f))
while True:
    pass