Thank you for your reply. I am compiling the source code for python 3.9.5 using Tools\msi\build.bat. But it said
Blockquote fatal error LNK1104: cannot open file “libffi-7.lib”
According to the original topic, I think there is something wrong with the code downloaded from https://www.python.org/ftp/python/3.9.5/Python-3.9.5.tgz. And there is no python 3.9.5 source code in GitHub - python/cpython: The Python programming language, so I put forward this problem.