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    <p>It's kinda hard to understand what you're trying to achieve from your post, but I'll try to give you examples on what I think you're trying to do.</p> <p>Let's begin by focusing on only <code>Box</code>-class, and ignore the <code>Item</code> for now. Here's what you have:</p> <pre><code>class Box(): id = 0 def __init__(self,id): Box.id = id def __get__(self): return Box.id </code></pre> <p>The <code>__get__</code> method is useless, simply don't use it here, you don't need it. Now what we notice, is you set <code>Box.id = 0</code>, this means that you can call <code>print(Box.id)</code> and it will print <code>0</code>. You can also init a new box instance, and you can call <code>print(box_instance.id)</code>, which will also print <code>0</code> as expected.</p> <p>However, in your <code>__init__</code> method, you change <code>Box.id</code>, instead of the instance's own id, is this what you meant to do? Here's a quick example on what will happen with your code:</p> <pre><code>In: Box.id Out: 0 a = Box(1) In: a.id Out: 1 In: Box.id Out: 1 b = Box(2) In: b.id Out: 2 In: a.id Out: 2 In: Box.id Out: 2 </code></pre> <p>As you can notice here (or test yourself), when initializing new <code>Box</code> object, it change's <code>Box</code> class' id, and not the id of the instance. This way every instance's id changes if you init a new <code>Box</code> -instance. This is caused cause it's not actually the id of the instance, but it's the id of <code>Box</code>.</p> <p>If this is the behavior you want, feel free to use it (you still don't need <code>__get__</code>), but if you want each Box to have their unique id, use <code>self</code> instead of box.</p> <pre><code>class Box: id = 0 # This is Box class' id, it's not even necessary to define it def __init__(self, id): # This will be each instance's unique id self.id = id #self.id means the instance's unique id </code></pre> <hr> <p>Now that we got the <code>Box</code> pretty much done, we can start working on the <code>Item</code>. I'm quite unsure of what you're trying to achieve with this, but taking a look at your code, it seems like you're actually trying to give each item an unique id (which is a good idea), and then you want to give them <code>box_id</code> which is simply <code>Box.id</code>, the class' id itself? This doesn't make any sense to me.</p> <p>What I ACTUALLY think you're trying to achieve: Insert items into boxes, and this way you want item to know it's "parent" box's id. It could be done as following:</p> <pre><code>class Item: #Notice how inheriting is not needed at all!! def __init__(self, id, parent): self.id = id self.parent = parent # I prefer calling it parent, call it what ever you want, box works too </code></pre> <p>Now what I'd also suggest, is:</p> <ol> <li>Inside <code>Box.__init__()</code>, define a list <code>self.items = []</code></li> <li>Inside <code>Item.__init__()</code>, append <code>self</code> to parent's items. <code>self.parent.items.append(self)</code></li> </ol> <p>This way your items know the box they're in, and boxes know which items are in them.</p> <hr> <p><strong>Edit:</strong> A short example code on how to use the parent:</p> <pre><code>box1 = Box(1) #box1 has id of 1 box2 = Box(2) #box2 has id of 2 item1 = Item(3, box1) #item1 has id of 3, parent box1 item2 = Item(4, box2) #item2 has id of 4, parent box2 item3 = Item(5, box1) #item3 has id of 5, parent box1 In: item1.id Out: 3 In: item1.parent.id Out: 1 In: item2.id Out: 4 In: item2.parent.id Out: 2 In: item3.id Out: 5 In: item3.parent.id Out: 1 In: item3.parent == item1.parent Out: True </code></pre> <p>As we see here, item can directly call it's parent's methods and use it's attributes. This way you can have multiple items in a box, (<code>item1</code> and <code>item3</code> both have same parent) and each of those items' <code>parent</code> attribute points to the box.</p> <p>Basically <code>item1.parent == box1</code> so <code>item1.parent.id</code> is what you called <code>item.box_id</code> in your code.</p>
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    1. POHow to get the parent Id of the child automatically
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    1. COHow do I know the parent. In the actual problem, i don't know the parent of the Item, I want the program to inherit it's parent id from the program. I did it, but it gets to the latest defined parent. To say in terms of your code, I exactly want the output of `a.id` to be 1.
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    2. COYou will need to pass the parent as a parameter - there's no better way of doing this. Why are you against it?
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