不确定我是否缺少明显的内容，但是为什么2个等效对象（在这种情况下为字符串）在python2和python3中具有不同的内存大小？
例如
Python 2.7.12 |Continuum Analytics, Inc.| (default, Jul 2 2016, 17:42:40)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
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>>> import sys
>>> sys.getsizeof('Hello World')
48
Python 3.6.0 |Continuum Analytics, Inc.| (default, Dec 23 2016, 12:22:00)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.getsizeof('Hello World')
60