小结
1、cpy的垃圾回收会对调用__del__多次；pypy仅仅一次；
https://www.liaoxuefeng.com/wiki/1016959663602400/1016966024263840
PyPy是另一个Python解释器，它的目标是执行速度。PyPy采用JIT技术，对Python代码进行动态编译（注意不是解释），所以可以显著提高Python代码的执行速度。
绝大部分Python代码都可以在PyPy下运行，但是PyPy和CPython有一些是不同的，这就导致相同的Python代码在两种解释器下执行可能会有不同的结果。如果你的代码要放到PyPy下执行，就需要了解PyPy和CPython的不同点。
https://pypy.readthedocs.io/en/latest/cpython_differences.html
There are a few extra implications from the difference in the GC. Most notably, if an object has a __del__, the __del__ is never called more than once in PyPy; but CPython will call the same __del__ several times if the object is resurrected and dies again (at least it is reliably so in older CPythons; newer CPythons try to call destructors not more than once, but there are counter-examples). The __del__ methods are called in “the right” order if they are on objects pointing to each other, as in CPython, but unlike CPython, if there is a dead cycle of objects referencing each other, their __del__ methods are called anyway; CPython would instead put them into the list garbage of the gc module. More information is available on the blog [1] [2].