Hi, ptrblck. I am so glad you give me a reply. Thanks!
I have been updated my Pytorch to v1.4 and rerun the code in Python2.7 and 3.7 respectively. As you have been said, I also get similar values in two Python environment. It seems like Pytorch have been fixed this problem as they update the version.  But I still don’t know why this issue happens. Maybe some computations in  C++ are different?