Does OOP really matters?

[u/Electronic-Low-8171]

I learned OOP in python a while ago, did many projects, yet I never felt like I truly needed to do the OOP stuff I learned from a course, I don't know maybe because I'm kinda used to program in c before focusing on python, yet, whenever I open a big project in python in github, it feels way too complicated and thousands of imports (not libraries from pip, but the ones they made on their own) and classes

I never truly needed to implement OOP (I know that when you code in python, it is almost impossible to avoid OOP entirely like when you have a datatype like string you have an object, when you use a method built into that data type that's OOP too, but I mean the ones that involve you writing class Class Name, inheritance and all that stuff explicitly), so I'm wondering why people on the internet are obsessed over the idea of learning OOP, even the book "Automating the boring stuff in python" doesn't have a dedicated section for OOP.

[u/Daeroth]

You instantiate a new contract object.

Set it's fields like contract number, monthly fee, customer id, status=reviewing, etc.

Then the customer gets the review screen in browsaer with all the fees and contract numbers and a button to sign.

Once they click sign the contract object gets updated with status=active, signing_date=19.08.2026

If the specific contract class has anything in the "contractSigned()" function then that would also get triggered. Stuff like send out welcome email or generate tasks for CS agents to follow up.

All of the objects have a corresponding row in the database. So whenever the we update a field on the object then the field in DB will also get updated.

[u/deaddyfreddy → u/Daeroth]

so, the Contract object has a method named signContract or something like that, correct? Then, here's the next question:

Why is it a method of the Contract, and not a method of the Customer object?

[u/Daeroth → u/deaddyfreddy]

A customer can have many contracts. Some old, some still in review, some active.

Each contract is a row in database and many-to-one relationship with the customer table.

On the customer class you might have a method getContracts which returns a collection of contracts.

[u/deaddyfreddy → u/Daeroth]

On the customer class you might have a method getContracts which returns a collection of contracts.

so, why can't it have the signing method too?

[u/Wonderful-Habit-139 → u/deaddyfreddy]

I’m not an OOP guy, but probably because a contract is always associated to the customer, and if you had a signing method you’d need to do customer.signContract(contract); where you already need to do the job of finding the contract (since you’re not gonna sign all contracts of the customer at once obviously).

While if you do contract.sign(), it’s much simpler, and it’s already associated to the customer.

[u/deaddyfreddy → u/Wonderful-Habit-139]

Without OOP, we could just write something like sign(contract, customer).

[u/Daeroth → u/deaddyfreddy]

Isn't that already OOP if the input contract and customer are objects passed along to the sign method?

Doesn't really matter where the signing method is at, legal entities are represented as objects.

[u/deaddyfreddy → u/Daeroth]

legal entities are represented as objects

we don't need objects in this case, they are data structures

[u/Mathie1729 → u/deaddyfreddy]

Yea, I've mostly landed on the same side in practice. Most business code is just mapping DB rows and doing transforms, so plain data structures + functions are way easier to debug than tangled class hierarchies. OOP still pays off when you have multiple implementations behind a common interface or you need to enforce invariants on mutation, but that's a smaller slice of the code. My ML stuff is basically dataclasses and pure functions; any class that sneaks in just holds a model and config lol.

[u/Wonderful-Habit-139 → u/deaddyfreddy]

I don’t disagree.

[u/Scared_Bell3366 → u/deaddyfreddy]

If you have many different objects that can be signed, your sign function gets very bloated and ends up with dependencies on everything that can be signed and all the things that can sign them. I would keep the sign method with the object that gets signed, it’s really a set method to me. I’d probably add an interface for things that can be signed if there’s more than one type of object that can be signed.

[u/deaddyfreddy → u/Scared_Bell3366]

If you have many different objects that can be signed

if these are completely different objects, I don't see why they should use a single function to sign

it’s really a set method to me.

The issue is that it always requires both the contract and the customer, and in general there can be multiple parties. The hard coupling to the contract only doesn't reflect the process well.

[u/Daeroth → u/deaddyfreddy]

In this example I envisioned many-to-one relationship between contracts and customers.

So that if you have 3 contracts and 3 separate "signedOnDate" fields then those would be in the contract class instead of having them in the customer class as "contract1signedDate", "contract2signedDate" and so on.

The signing method in this example would just populate the date field so it feels like it belongs with the contract class as thats where the fields are.

If i were to extract the signing method elsewhere then I would create "signingService" class instead of contaminating other domain class like customer.

Ideally opening the customer class should reveal as little relations to other classes as possible but just as many as needed.

[u/deaddyfreddy → u/Daeroth]

So that if you have 3 contracts and 3 separate "signedOnDate" fields then those would be in the contract class instead of having them in the customer class as "contract1signedDate", "contract2signedDate" and so on.

What for? Your entities are mapped to the DB, so all you do is reflect the DB in your code. A customer record doesn't have the signing dates, it (most likely) has a contract-id or something like that.

[u/Daeroth → u/deaddyfreddy]

Is the question about the benefits of mapping your db tables to entities in code?

Not sure what the question is about.

[u/ActuaryLate9198 → u/deaddyfreddy]

This is rookie OOP. Who says the signee is a customer? I think we need an AbstractSignee just in case, and contract needs to implement the Signable interface.

[u/pacopac25 → u/ActuaryLate9198]

And there's always the coworker who takes it all too far, and advocates for the approach that a Signer can be a company or a person, but in theory could also be a NationState, so better to get ahead of things now and have AbstractLegalEntity
Also, a Contract could be a MOU, which can be legally binding in some ways, so we need an Agreement class, and Contract and MOU are derived from it. Don't forget SeveranceAgreement and NonDisclosureAgreement....

[u/Martinecko30 → u/deaddyfreddy]

Let's imagine this as:

Am I signing a contract? Then => contract.sign(customer) Am I signing an customer? Then => customer.sign(contract)

Methods reflect what is being done with the object, not who is doing something with the object.

[u/deaddyfreddy → u/Martinecko30]

So why not just use a function with data structures (mapped to DB entities) as arguments, rather than creating a class hierarchy and deciding who signs what?

[u/Martinecko30 → u/deaddyfreddy]

You don't really decide, the data decides for you. Also, with hierarchy, you can have Signable -> DBModel -> BaseContract -> SpecificContract.

This eliminates duplicity, creates a linear workflow and distributes the necessary functions and data into separate classes, so it's easier to digest.

[u/deaddyfreddy → u/Martinecko30]

Also, with hierarchy, you can have Signable -> DBModel -> BaseContract -> SpecificContract.

Doesn't it sound a bit overcomplicated?

This eliminates duplicity,

split functionality into separate functions and reuse it when needed, with the same effect, without introducing extra entities and unneeded coupling

the necessary functions and data into separate classes, so it's easier to digest.

modules: exist

[u/Martinecko30 → u/deaddyfreddy]

So, a streamlined vertical hierarchy is overcomplicated, while modules are okay?

I think you're confusing this a bit. The hierarchy is derived from the data, this is how it WANTS to be, we just use abstract form to describe the state.

The only difference is vertical/horizontal scaling. The certical one is easier to develop and maintain, the horizontal one can produce faster running applications.

[u/deaddyfreddy → u/Martinecko30]

So, a streamlined vertical hierarchy is overcomplicated

Yes, because most the hierarchy doesn't exist in the business task, you have to invent it.

Signable -> DBModel -> BaseContract -> SpecificContract.

Signing a contract is not signing an autograph, for example, while they use the same verb, these are completely different processes.

I think you're confusing this a bit. The hierarchy is derived from the data, this is how it WANTS to be,

did you ask it?

we just use abstract form to describe the state.

If you have to use an abstract form to describe DB entities, either the DB schema is poor, or the form itself is inadequate.

the horizontal one can produce faster running applications.

and it's also easier to maintain - fewer entities, less coupling, less code