In Python, what is the reference count of cyclic reference and why?

Question

Here is a example of a cyclic reference of Python.

>>> a = [1]
>>> b = [2]
>>> a.append(b)
>>> b.append(a)

after this,

>>> sys.getrefcount(a) = 3
>>> sys.getrefcount(b) = 3

Why do a and b have a reference count of 3??

Sorry guys i just took a mistake.

the real question is the different one.

>>> GNU = ['is not Unix']
>>> GNU.insert(0, GNU)
>>> sys.getrefcount(GNU) = 4

Why is the reference count of 'GNU' is 4 ?

Thanks in advance :)

Answer 1

There are 3 references to each:

1. In the other's list in the first element.
2. As an argument to sys.getrefcount().
3. The current scope, i.e. bound to a and b.