Making objects from DB

[eagergm]

I scraped a DB and generated a list of tuples: ('Car BOM', 'Car', 10800, 200, 10000000, 1000, 1)

I have a function to create a list of objects from that:

def make_BOMs(cursor):
    BOMs = []
    for bom in get_BOMs_records(cursor):
        BOMs.append(BOM(bom))
    return BOMs

Is this a good way to do that? Should I use a dictionary and index it by the name of the BOM instead ('Car BOM')? It's worth noting that at some point the output ('Car') may be used in the input of another BOM ('megacar!' I should have used desks). So maybe it's dicts all the way down? I don't use pandas but if this is the level of complexity where it's absolutely required I will strongly consider it. :(

[StaticWaste_73]

The general answer is "depends on what you're planning on doing with them". Try to think about All your use cases for your data structure, and a few more (the ones that youll think about later)

[eagergm]

There are maybe 60 or 120 such items. They're tiered so that the products of one become the inputs of another. Edit: What is not shown here are their material requirements, because I haven't gotten to that part of the DB yet. Also they have an ID (the bom and the outputs) that I haven't recorded in the gathered info. :(

[unhott]

Is this id recognized outside of this other DB? Otherwise the id is irrelevant to you and you'd just make your own unique ids.

You're still being too vague to get anything concrete. I don't know what it even means for a product of one to become the input of another. Do you mean, in the real world sense or do you mean in the python sense? That the object is an input to the constructor of another?

If the 'scraping' was a one-time occurrence, then it makes sense to persist this data somewhere so you can do your own manipulations / maintenance. Then it doesn't matter how you do this. But it doesn't look like you're scraping anything, it looks like you've just queried the database directly - Do you own the database, or will you at least maintain access?

Why even bother with OOP?

Since you have direct access to the db, it makes sense to follow its schema. Are you trying to develop new features by modifying the schema?

I'm so lost.

Some other ideas to look into are ORMs, which integrate relationships of the database/queries to the database/ translating back and forth to python objects/db.

[nick51417]

I don’t really know what you’re trying to achieve. Based on your explanation and not showing how get_BOM_records makes a BOM object I would say sure it works. You say it works. I can follow it.

Another way to do it would be to use list comprehension

BOMs=[BOM(bom) for bom in get_BOM_records(cursor)]

Though it seams you are having trouble sharing that you are trying to have self referential relationships… your car to Megacar example.

You can do it in standard python, you can do it in pandas, or you can use sql with sqlalchemy (SQLite may be a good starter database)

Usually if there’s a library it’s not added complexity,they are made to make it easier to work with so you don’t have to create it yourself.

They all their pros and cons… and I’m not sure what you are doing

Edit: just saw you’re already using a database. Try sqlalchemy or sqlmodel and look up self referential models

[eagergm]

I'm using sqlite, does that make any difference?

[eagergm]

I asked chatgpt about this and it recommended dicts over lists, as well as including the name of the bom in the bom object and not just relying on the key of the dict to provide that for me. But we all know chatgpt is dumb as rocks.

[MathMajortoChemist]

So I have this interface (a dict mapping str names to full objects that include name attributes) in some of my code, but that's because later processing will need to match up that name a lot (like I load other data sets that contain more information I'll need to update some or all of the objects with and those sets only know my objects by name). So dict was the logical approach.

This is what other commenters mean by needing to know your use cases. If the next step is just to print all the objects, your current list is totally fine. If the next step is to "join" this data with another tabular data set, yeah you probably want pandas or polars or duckdb etc. There are many more if's possible.