col speed wrote:
I was just thinking about the immutability of things and tried this
(which -at least I- find interesting:
id(1)
154579120
a = 1
id(a)
154579120
a += 2
id(a)
154579096
id(3)
154579096
a is 3
True
Although there is probably no other logical way of doing it - I learnt
something new again!
Prepare to have your mind boggled:
py> a = 99
py> b = 99
py> a is b
True
py> a = 9912345
py> b = 9912345
py> a is b
False
Well, okay, so it's not *much* of a boggle. Perhaps a bogglet.
What happens is that Python caches the small integers, like -1, 0, 1, up to
some limit, and re-uses them when and as needed. That limit various from
version to version, so you can't rely on it. But larger integers are not
cached, and so you get a fresh one each time.
This makes sense, and is easy to understand. Now for the real boggle:
py> a = 9912346; b = 9912346
py> a is b
True
Can you guess what is going on here?
(Answer will follow later.)
--
Steven
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