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

>>>