[Python源码剖析]字符缓冲池intern机制

static PyStringObject *characters[UCHAR_MAX + 1];
...

/* This dictionary holds all interned strings.  Note that references to
   strings in this dictionary are *not* counted in the string‘s ob_refcnt.
   When the interned string reaches a refcnt of 0 the string deallocation
   function will delete the reference from this dictionary.

   Another way to look at this is that to say that the actual reference
   count of a string is:  s->ob_refcnt + (s->ob_sstate?2:0)
*/

>>> len(locals().keys())
4
>>> for i in range(256):
...     locals()[‘a%s‘%i]= str(i)
...
>>> len(locals().keys())
261
>>> a=‘247‘
>>> id(a247)
4301254088
>>> id(a)
4301235264
>>>