By the way, this surprised me. Would anyone like to explain this?

    >>> id(f()), id(f())
    (139927013695536, 139927013695536)

That made me think. The result of the first f() has gone out of scope by the time the second call, and so the id (that is, the memory) is available next time CPython needs a place for an int of about the same bit_length.

>>> def f(): return 10**1000

>>> def g(): return 9**1048

>>> id(f()), id(g())
(2149044150320, 2149044150320)

Neat demonstration that the id of an object is only unique in its lifetime.

Jeff