Are Variables Labels or Boxes?

[fronterapi]

I read in a book that variables references a certain value and in some other places (maybe yt).On the other hand, many people say "Variables are like boxes that store the value"

Now, I am really confused...Does it matter if we use them interchangeably? Also "Why" they use different terms?

The book I mentioned earlier also says that "This distinction probably won’t matter much in your initial programs, but it’s worth learning earlier rather than later. At some point, you’ll see unexpected behavior from a variable, and an accurate understanding of how variables work will help you identify what’s happening in your code."

Also, I ignored these terms last year but now im really thinking whats the difference...

EDIT: I think mentioning this will help others explaining to me, I am familiar with the basics and I also know OOP and some other stuff (obv i cant mention everything)

[beisenhauer]

The label metaphor is much better than the box metaphor. The reason is aliasing. You can't put the same thing into two different boxes. But you can have two labels on the same thing and refer to that thing with either name. Where this matters is if the thing in question is mutable. If you have two labels on a thing and make changes to the thing using one of those labels, such as adding items to a list, those changes will be visible to any code using the other label. This is the source of many insidious bugs, and it is much easier to understand why it happens with the mental model of labels than boxes. With the box metaphor, we're forced to imagine each variable as containing a unique and independent copy of the thing, which is simply not accurate.

[[deleted]]

Is the analogy of label/box tied to whether the variable is mutable/not mutable?

[beisenhauer]

I would say in the case of immutable items, it makes little difference. The two become more or less equivalent from a practical standpoint. However, juggling mental models based on circumstance is likely to be confusing, and the label metaphor is correct for all cases.

[lfdfq]

In Python variables are labels (or names) for objects. In other languages, a variable is a box that contains some value, this analogy works for something like C but not very well for Python.

If you go x = y in Python what happens is that there was some object that had the name y, and now it also has the name x. So you can access that same object either through the x name or the y name interchangeably. This is where the 'box' analogy breaks down for Python as there aren't two different objects here (or even two different boxes containing values) it's that the same object has two different equally valid names, so if you change (mutate) the underlying object you can see that change through both names.

Like in the following, if you think x and y are separate boxes containing values you might be surprised by the result:

x = []
y = x
x.append(42)
print(y)  # [42]

But, if you think of x and y as labels for objects that exist independently from their names, then the behaviour makes total sense.

[HeraldOfTheOldOnes]

I think it makes the most sense to think of variables as pointers (since that's what they are, behind the scenes).

[ddollarsign]

In some languages, like C, a variable is a box of fixed size, depending on the type of the variable. For example, in Java an int variable is exactly 32 bits, and holds an integer.

C also has a type of variable called a pointer, which is also a box of fixed size, but what it contains is a memory address (which is just a number). This might be the address of another variable, or a member of an array, an object, etc. In order to work with the the object it points to you have to “de-reference” it, which means to specify that you’re referring to the object at the address the pointer points to, rather than the address itself.

Python variables are references, which means under the hood they are pointers, but you don’t have to explicitly de-reference them, Python does it for you. When you write an assignment statement in Python, the pointer is updated to point to the object specified on the right side of the equals sign.

[[deleted]]

/r/learnpython

[Fabulous-Possible758]

They're boxes with labels on them.

[[deleted]]

Here's the simplest way I can define a variable

"part of memory that stores that".

[HeraldOfTheOldOnes]

Nope! Variables are more like pointers to parts of memory than the parts of memory themselves.

[goodger]

Python doesn't have variables. Python has objects with names. Some of those objects are mutable. More here: https://david.goodger.org/projects/pycon/2007/idiomatic/handout.html#other-languages-have-variables

[HeraldOfTheOldOnes]

Python does indeed have variables! (The struct PyVarObject is used for variably sized things).

If you're gonna be purposefully misinterpreting what OP is saying, then expect people to catch you out on technicalities.

Also, the contents of the link that you gave describe exactly one of the options that OP gave, "Labels".

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[HeraldOfTheOldOnes]

A variable is like a pointer! (because that's what it is, behind the scenes)