Python 3.9.0 出了：「Python 3.9.0 is now available, and you can already test 3.10.0a1!」。
下一個版本是 3.10 而非 Python 4：
OK, boring! Where is Python 4?
Not so fast! The next release after 3.9 will be 3.10. It will be an incremental improvement over 3.9, just as 3.9 was over 3.8, and so on.
在「What’s New In Python 3.9」裡面的「Optimizations」這段有測一些基本操作的效能，可以看到 Python 3.9 其實比 Python 3.8 慢了一些？好像也沒有提到原因就是了...
https://docs.python.org/release/3.9.0/whatsnew/3.9.html#new-parser
3.9 效能略差於 3.8 好像和採用新的 parser 有關？
>>>The new parser’s performance is roughly comparable to that of the old parser, but the PEG formalism is more flexible than LL(1) when it comes to designing new language features.