Understanding sys.getrefcount

Asked Jul 07 '14 at 15:29

Active Jul 07 '14 at 16:15

Viewed 45 times

From the doc:

The count returned is generally one higher than you might expect, because it includes the (temporary) reference as an argument to getrefcount().

And 'till here all is clear to me, infact:

Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> x = 'hello'
>>> sys.getrefcount(x)
2

But if I do something like this:

>>> import sys
>>> x = 'hello'
>>> sys.getrefcount(x)
2
>>> sys.getrefcount('hello')
3

I don't understand why I get 3, should I get 2?

Another strange example to me that I have noticed (from a file .py):

import sys
print(sys.getrefcount(59587389257548905723958375385))

Result ---> 3

Should't it be 1 (according to the doc)?

edited Jul 07 '14 at 16:15

asked Jul 07 '14 at 15:29

zer0uno

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Maybe because of `'hello'`? – Maroun Jul 07 '14 at 15:30
but I'm asking the reference count of `'hello'` and only a variable references to it – zer0uno Jul 07 '14 at 15:32
You create one reference to `'hello'` for the variable `x` and another reference in the call to `getrefcount`. – Matthias Jul 07 '14 at 15:36
And the result should be 2, don't you think? – zer0uno Jul 07 '14 at 15:38
Interestingly, `import sys; sys.getrefcount("hello")` gives `3`, even without assigning to x or anything. – Kevin Jul 07 '14 at 15:39
Yes, I tried with every number and string I could, even without before assignign each of them to a name the result is always 3 – zer0uno Jul 07 '14 at 15:40
The instance of the string that contains the text `'hello'` is being reused. – Jeff Mercado Jul 07 '14 at 15:40
@JeffMercado could you explain better? – zer0uno Jul 07 '14 at 15:41
This is just a REPL specific behavior, try with normal Python code and it'll work fine. – Ashwini Chaudhary Jul 07 '14 at 15:54
Atleast the first part is probably a duplicate of: http://stackoverflow.com/questions/15541404/python-string-interning – Bill Lynch Jul 07 '14 at 15:59
@undefinedisnotafunction what do you mean with normal Python code? I'm get typing normal python code – zer0uno Jul 07 '14 at 16:02
@antox In a .py file. – Ashwini Chaudhary Jul 07 '14 at 16:03
@undefinedisnotafunction And I tried it, I always get 3 – zer0uno Jul 07 '14 at 16:04

Understanding sys.getrefcount

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