How to create a list of variable references in Python?

Question

I am using Python 3. Suppose I have 2 variables and create a list containing the 2 variables

a = 48
b = 42
arr = [a, b]

If I modify a then arr remains the same, this is because a is an integer, if it was an object, then the object in arr (that is technically a reference to the same object) gets updated. I want arr[0] to be a reference to the variable a rather than the value itself, so that if a is changed then arr[0] is changed as well. How do I do that?

You're trying to understand mutability. See this answer stackoverflow.com/questions/9172263/…. — vanPelt2
– vanPelt2, Commented May 22, 2020 at 15:46
"a reference to the variable a" There is no such thing in Python. Can you clarify what behaviour you want? Are a and b function locals or globals? Do you always need a list of "variable references", or also independent references? Do you need a and arr to appear "normal", or is a wrapping helper object acceptable? — MisterMiyagi
– MisterMiyagi, Commented May 22, 2020 at 16:06
a and b are globals, and I want them to appear normal @MisterMiyagi — Shree Singhi
– Shree Singhi, Commented May 22, 2020 at 16:21

Alexander Pushkarev · Accepted Answer · 2020-05-22 15:57:16Z

1

Unfortunately, it is not possible. Since integer is immutable type, whenever you change integer value, you essentially create new object.

You can check this:

>>> a = 48
>>> b = 42
>>> arr = [a, b]
>>> id(a)
263256736
>>> id(arr[0])
263256736
>>> a = 11
>>> id(a)
263256144 # it is a new object already
>>> id(arr[0])
263256736 # still points to the old object

answered May 22, 2020 at 15:57

Alexander Pushkarev

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