About the changing id of an immutable string

Question

Something about the id of objects of type str (in python 2.7) puzzles me. The str type is immutable, so I would expect that once it is

Answer 1

So while Python is not guaranteed to intern strings, it will frequently reuse the same string, and is may mislead. It's important to know that you shouldn't check id or is for equality of strings.

To demonstrate this, one way I've discovered to force a new string in Python 2.6 at least:

>>> so = 'so'
>>> new_so = '{0}'.format(so)
>>> so is new_so 
False

and here's a bit more Python exploration:

>>> id(so)
102596064
>>> id(new_so)
259679968
>>> so == new_so
True